WO1999016420A1

WO1999016420A1 - Stabilized preparations for use in nebulizers

Info

Publication number: WO1999016420A1
Application number: PCT/US1998/020603
Authority: WO
Inventors: Ernest G. Schutt; Thomas E. Tarara; Luis A. Dellamary; Alexey Kabalnov; Jeffry G. Weers
Original assignee: Inhale Therapeutic Systems, Inc.
Priority date: 1997-09-29
Filing date: 1998-09-29
Publication date: 1999-04-08
Also published as: WO1999016420A9

Abstract

Stabilized dispersions are provided for the delivery of a bioactive agent to the respiratory tract of a patient. The dispersions preferably comprise a stabilized colloidal system which may comprise a fluorochemical component. In particularly preferred embodiments, the stabilized dispersions comprises perforated microstructures dispersed in a fluorochemical suspension medium. As density variations between the suspended particles and suspension medium are minimized and attractive forces between microstructures are attenuated, the disclosed dispersions are particularly resistant to degradation, such as by settling or flocculation. In particularly preferred embodiments, the stabilized dispersions may be administered to the lung of a patient using a nebulizer.

Description

STABILIZED PREPARATIONS FO R U SE IN NEBULIZERS

Field of the Invention

The present invention generally relates to formulations and methods for the administration of bioactive agents to a patient via the respiratory tract More particularly, the present invention relates to methods, systems and compositions comprising relatively stable dispersions that are preferably administered via nebulization both for topical delivery to the lung, and for delivery via the lung to the systemic circulation.

Backorouπd of the Invention

Targeted drug delivery means are particularly desirable where toxicity or unavailability of the pharmaceutical compound is an issue. Specific drug delivery methods and compositions that effectively deposit the compound at the site of action potentially serves to minimize toxic side effects lower dosing requirements and decrease therapeutic costs. In this regard, the development of such systems for pulmonary drug delivery has long been a goal of the pharmaceutical industry.

The three most common systems presently used to deliver drugs locally to the pulmonary air passages are dry powder inhalers (DPIs), metered dose inhalers (MDIs) and nebulizers. MDIs, the most popular method of inhalation administration, may be used to deliver medicaments in a solubilized form or as a dispersion Typically, MDIs compnse a Freon or other relatively high vapor pressure propellant that forces aerosolized medication into the respiratory tract upon activation of the device. Unlike MDIs, DPIs generally rely on the patient's inspiratory efforts to introduce a medicament in a dry powder form to the lungs. Finally, nebulizers form a medicament aerosol to be inhaled by imparting energy to a liquid solution More recently, direct pulmonary delivery of drugs dunng liquid ventilation or pulmonary lavage using a fluorochemical medium has also been explored. While each of these methods and associated systems may prove effective in selected situations, inherent drawbacks, including formulation limitations, can limit their use.

A key development, which has elevated the importance of pulmonary drug delivery systems, has been the emergence of new drugs deπved from biotechnology (e.g. peptides, proteins, oligonuclεotides and plasmids) The systemic delivery of these biopolymers has proven difficult, owing to their large molecular size, high surface charge, poor chemical and enzymatic stability, and low permeability across vaπous absorption barπers of the body Because of their low bioavailability by oral and transdermal routes of administration, drugs such as peptides are currently administered pnmaπly by infusions or frequent injections. The development of less invasive methods for delivenng peptides and other biopolymers represents a large focus of current drug delivery research, and a number of sites of administration are being explored, including enhanced oral, nasal, and pulmonary delivery As indicated above, nebulizers are frequently used for drug delivery to the human lung and are particularly useful for the treatment of hospitalized or nonambulatory patients There are two mam classes of devices air jet nebulizers and ultrasonic nebulizers In air jεt nebulizers compressed air is forced through an orifice A liquid may then be withdrawn from a perpendicular nozzle (the Bernoulli effect! to mix with the air jet to form droplets. A baffle (or series of baffles) within the nebulizer is used to facilitate formation of the aerosol cloud In contrast, ultrasonic nebulizers rely on the generation of ultrasound waves in an ultrasonic nebulizer chamber by a ceramic piezoelectric crystal that vibrates at a precise frequency when electrically excited The ultrasonic energy sets up high energy waves in the nebulizer solution, facilitating generation of an aerosol cloud.

Formulations for nebulization typically comprise aqueous based solutions Assuming that the solubility and stability of the active drug are adequate, an aqueous based formulation administered by nebulization is reasonable when the estimated minimal effective dose exceeds about 200 μg Continuous nebulization has long been an option for the delivery of topical lung therapy for the treatment of various lung diseases such as asthma, chronic obstructive pulmonary disease, emphysema, and bronchitis More recently, proteins such as DNase have been delivered by conventional jet nebulizers for their local effect on the lung Unfortunately, continuous nebulization is an intnnsically inefficient way to deliver aerosolized medication This fact is underscored by the observation that doses of bronchodilators delivered using nebulizers are three orders of magnitude greater than a bioequivalent dose delivered by MDI or dry powder generator. In addition to concerns with respect to device efficiency, concerns also exist with regards to changes in the formulation dunng the nebulization process. For example, drug concentration in the reservoir solution of an air jet nebulizer often increase over time Moreover, a change in drug concentration may imply a change in osmolality of the aqueous solution, and hyperosmolar nebulizer solutions have been shown to cause bronchocoπstπctioπ

In terms of pulmonary delivery of bioactive agents to the systemic circulation via nebulization, most of the research has focused on the use of portable hand held ultrasonic nebulizers also referred to as metered solution nebulizers These devices should not be confused with hand held nebulizers which require several minutes per treatment These devices, generally known as single bolus nebulizers, aerosolize a single bolus of medication in an aqueous solution with a particle size efficient for deep lung delivery in one or two breaths These devices fall into three broad categories

The first category compnses pure piezoelεctπc single bolus nebulizers such as those described by Mutterlein, et al , (J Aerosol Med 1988, 1 231 ) In another category, the desired aerosol cloud may be generated by microchannel extrusion single bolus nebulizers such as those described in U S Pat No 3,812,854 Finally, a third category comprises devices exemplified by Robertson, et al , (WO 92111050) which descnbes cyclic pressunzation single bolus nebulizers Each of the aforementioned references is incorporated herein in their entirety

While such devices are an improvement over conventional hand held nebulizers that require treatment times of several minutes, they are somewhat limited by the fact that they employ multidose reservoirs This is problematic for protein delivery applications where the product must remain sterile throughout the therapy program At the very least use of these multidose reservoirs would require the use of preservatives, and even this approach is unlikely to be satisfactory under all product usage sceπaπos. In order to overcome some of these limitations, a unit dose system has recently been descnbed by Schuster, et, al , (Pharm Res. 1997; 14-354 which is incorporated herein). However, problems remain even with such unit dose systems. For example, a pitfall with devices for the delivery of bioactive agents to the systemic circulation is that the bioactive agent must have long term stability in an aqueous phase. This is possible only for a select few peptides and proteins.

Accordingly, it is an object of the present invention to provide methods, compositions and systems for the effective pulmonary delivery of bioactive agents using nebulizers.

It is a further object of the present invention to provide methods and compositions for the stabilization of bioactive agents to be delivered using a nebulizer.

It is yet another object of the present invention to provide methods and preparations that advantageously allow for the efficient delivery of bioactive agents to the systemic circulation of a patient in need thereof.

Summary of the Invention These and other objects are provided for by the invention disclosed and claimed herein To that end, the methods and associated compositions of the present invention provide, in a broad aspect, for the improved delivery of bioactive agents using stabilized preparations. Preferably, the bioactive agents are delivered to a patient via the respiratory tract. More particularly, the present invention provides for the formation and use of stabilized dispersions (also referred to as stabilized respiratory dispersions) and inhalation systems, including nebulizers comprising such dispersions, as well as individual components thereof. Unlike prior art formulations in a form for use in nebulizers, the present invention preferably employs novel techniques to reduce attractive forces between the dispersed constituents and to reduce density fluctuations in the stabilized dispersion thereby retarding degradation of the disclosed preparations by flocculation, sedimentation or creaming. Moreover, the stabilized preparations of the present invention preferably compnse a suspension medium that further serves to reduce the rate of degradation with respect to the incorporated bioactive agent. In particularly preferred embodiments, the suspension medium will compnse a fluoπnated compound or fluorocarbon. Those skilled in the art will appreciate that the disclosed stable preparations, and systems comprising those preparations, act to reduce dosing incongruities, thereby facilitating uniform drug delivery, allowing for more concentrated dispersions and, retarding the degradation of any labile biopolymers incorporated therein.

In a broad sense, the stabilized dispersions of the presεnt invention incorporate colloidal preparations compπsing a nonaqueous continuous phase wherein the stabilized dispersions are capable of being nebulized or aerosolized to provide effective dosing to a patient in need thereof. For example, the stabilized dispersions may comprise any reverse emulsion or particulate dispersion that allows for the effective delivery of a bioactive agent to the pulmonary air passages of a mammal. Those skilled in the art will appreciate that, the disperse phase of such preparations may comprise liquid particulates in the case of reverse emulsions or non liquid particulates in the case of stabilized suspensions Accordingly, for the purposes of the present application the term "stabilized dispersion" shall be held to compnse colloidal systems compπsing reverse emulsions and particulate suspensions unless otherwise dictated by contextual constraints With respect to each of these cases, the stabilized dispersion may be used with a nebulizer to provide the desired aerosolized medicament for pulmonary administration

With regard to particularly preferred embodiments, the stabilized preparations of the present invention provide these and other advantages through the use of particulate suspensions compπsing hollow and/or porous perforated microstructures that substantially reduce attractive molecular forces, such as van der Waals forces, which dominate prior art dispersion preparations More particularly, the use of perforated (or porous) microstructures or microparticulates that are permeated or filled by the surrounding fluid medium, or suspension medium, significantly reduces disruptive attractive forces between the particles. Additionally, the components of the dispersions may be selected to minimize differences in polanzabilities d e reduced Hamaker constant differentials) and further stabilize the preparation. The relatively homogeneous nature of thεse particulate dispεrsions or suspensions inhibits deterioration thereby allowing for pharmacεutical preparations having enhanced stability. In addition to the heretofore unappreciated advantages associated with the formation of stabilized particulate dispersions, the perforated configuration and corresponding large surface area enables the microstructures to be more easily carried by the flow of gases during inhalation than non perforated particles of comparable size This, in turn, enables the perforated microstructures or microparticles of the present invention to be carried more efficiently into the lungs of a patient than non perforated structures such as micronized particles or relatively nonporous microspheres In view of these advantages, dispersions comprising perforated microstructures are particularly compatible with inhalation therapies compπsing administration of the bioactive preparation to at least a portion of the pulmonary air passages For the purposes of the present application, these stabilized dispersions intended for pulmonary drug delivery may be termed respiratory dispersions In particularly preferred embodiments, such respiratory dispersions are used in conjunction with nebulizers to effectively deliver a bioactive agent to the pulmonary air passages or nasal passages of a patient. For those embodiments comprising perforated microstructures, those skilled in the art will appreciate that they may be formed of any biocompatible mateπai providing the desired physical characteristics or morphology that allows for the preparation of stabilized dispersions In this respect, the perforated microstructures comprise pores, voids, defεcts or other interstitial spaces that allow the fluid suspεnsion medium to freely permeate, or perfusε, the particulate boundary, thus reducing or minimizing density differences between the dispersion components Yet, given thεse constraints, it will be appreciated that any mateπai or configuration may be used to form the microstructure matπx. With regard to the selected materials, it is desirable that the microstructure incorporates at least one surfactant Preferably, this surfactant will compnse a phospholipid or other surfactant approved for pulmonary use As to the configuration, particulariy preferred embodimεnts of the invention incorporate spray dned, hollow microspheres having a relatively thin porous wall defining a large internal void, although, other void containing or perforated structures are contemplated as well.

Accordingly, select embodimεnts of the invention provide for stable respiratory dispersions for use in a nebulizer compπsing a suspension medium having dispersed therein a plurality of perforated microstructures compnsing at least one bioactive agent wherein said suspension medium substantially permeates said perforated microstructures.

While preferred embodiments of thε invention compnse perforated microstructures, relatively nonporous or solid particulates may also be used to prepare dispersions that are compatible with the teachings herein. That is, respiratory dispersions compπsing suspensions of relatively nonporous or solid particulates in a nonaqeous suspension medium are also contemplatεd as being within the scope of the present invention In this respect, such relatively nonporous particulates may comprise micronized particles or nanocrystals. Accordingly, as used herein the term "particulate" shall be interpreted broadly to mean any non liquid particle comprising thε discontinuous phase of a dispersion or suspension. More specifically, it will be appreciated that the term "particulate" shall be held to comprise particles of any porosity, including both perforated microstructures and relatively nonporous particles.

It should further be appreciated that the nonaqueous continuous phase or suspension medium, may be any liquid or compound that is in liquid form, under appropriate thermodynamic conditions, for formation of a compatible particulate dispersion or reverse emulsion. Unless otherwisε dictated by contextual restraints, the terms "suspension medium," "suspension media" and "nonaqueous continuous phase" are held to be equivalent for the purposεs of the instant application and may be usεd interchangeably. For embodiments whεrεin the stabilized dispersion is to be used in conjunction with a nebulizer, the suspension medium preferably comprises hydrocarbons or fluorocarbons having a vapor pressure less than about one atmosphere. That is, it will preferably be a liquid under standard conditions of one atmosphεre and 25° C.

In accordance with the teachings herein, particularly preferred suspension mediums or nonaqueous continuous phases compnse fluorochemicals (e g pεrfluorocarbons or fluorocarbons) that are liquid at room temperature It is well established that many fluorochemicals have a proven history of safety and biocompatibility in the lung. Further, in contrast to aqueous solutions, fluorochemicals do not negatively impact gas exchangε. Moreover, because of their unique wettability characteπstics, fluorochemicals may be able to carry an aerosolized stream of particles deeper into the lung, thereby improving systemic delivery Finally, many fluorochemicals are also bacteπostatic thereby decreasing the potential for microbial growth in compatible nebulizer devices

As such, the presεnt invention provides for the use of a liquid fluorochemical in the manufacture of a medicament for the pulmonary delivery of a bioactive agent whereby thε mεdicameπt compπsεs a stabilized dispersion having a fluorochemical continuous phase which is nebulized using a nebulizer to form an aerosolized medicamεnt compπsing said bioactive agent wherein said aerosolized medicament is administered to at least a portion of the pulmonary air passages of a patient in neεd thεrεof. It will further bε appreciated that, in selected embodiments, thε presεnt invention compnses methods for forming dispersions which comprise combining a plurality of particulates compπsing at least one bioactive agent with a predetermined volume of suspεnsion medium, to provide a respiratory blend. The respiratory bland may then be mixed or otherwise agitated to provide a substantially homogeneous dispersion. Again, in preferred embodiments, the particulates will compnse perforatεd microstructures which allow for thε perfusion or permeation of thε sεlectεd suspεnsion medium.

Of course, in other embodiments the dispersion may compπsε a reverse emulsion.

As such, prefεrred εmbodimεnts of thε invention provide for the formation of stabilized respiratory dispersions compnsing the steps of. combining a plurality of perforated microstructures compπsing at least one bioactive agent with a predetermined volume of a nonaqueous suspension medium to provide a respiratory blend wherεin said suspension medium permeates said perforated microstructures; and mixing said respiratory blεπd to provide a substantially homogeneous respiratory dispersion.

Along with the aforementioned advantages, the stability of the formed particulate dispersions may be further increased by reducing, or minimizing, the Hamaker constant differential between incorporated particulates, or perforated microstructures, and the suspension medium Those skilled in the art will appreciate that Hamaker constants tend to scale with refractive indices. In this regard, the present invention further provides methods for stabilizing a respiratory dispersion by reducing attractivε van dεr Waals forces compπsing the steps of: providing a plurality of perforated microstructures; combining the pεrforatεd microstructures with a suspension mεdium comprising at lεast one fluorochemical wherein the suspension medium and the perforated microstructures arε selected to provide a refractive index differential value of less than about 0 5 In accordance with the teachings herein, the particulates preferably compose pεrforatεd microstructurεs and, in particularly preferred embodiments, the particulates will compnse hollow, porous microsphεres

With regard to de vεry of the stabilized preparations, another aspect of the present invention is directed to liquid inhalation systems for the administration of one or more bioactive agents to a patient. As such, the present invention provides for inhalation systems for the pulmonary administration of a bioactive agent to a patient comprising: a fluid reservoir, a stable respiratory dispersion in said fluid reservoir whεrein said stabilized dispersion composes a fluorochemical continuous phase and at least one bioactive agent; and a nebulizer operably associated with said fluid reservoir wherein the nebulizer is capable of aerosolizing and discharging the stable respiratory dispersion.

The respiratory dispersion may compnsε a revεrse emulsion, microemulsioπ or particulate suspension Preferably, the dispersion compnses a suspension medium having dispersed thεrein a plurality of pεrforated microstructures, which comprise at least onε bioactive agent and are substantially pεrmεatεd by thε suspension mεdium Those skilled in the art will appreciate that the nebulizer may compπsε an ultrasonic nebulizer, an air jet nebulizer and, most preferably, a single-bolus nebulizer. In any event, thε disclosed systems of the present invention allow for the reproducible administration of bioactive agents having aerosolized particle size small enough to travel deep within the lung More specifically, the aerosolized medicamεnt will preferably exhibit a fine particle fraction of greater than approximately 20% wlw.

Yet another associated advantage of the present invention is the effective pulmonary delivery of bioactive agents. As used herein, the terms "bioactive agent" refers to a substance which is used in connection with an application that is therapeutic or diagnostic in nature, such as methods for diagnosing the presεncε or absence of a disease in a patient and/or methods for treating disease in a patient. As to compatible bioactive agents, those skilled in thε art will appreciate that any thεrapeutic or diagnostic agent may be incorporatεd in the stabilized dispersions of the present invention For example, the bioactive agent may be selected from the group consisting of antiallergics, bronchodilators, bronchoconstπctors, pulmonary lung surfactants, analgesics, antibiotics, leukotnene inhibitors or antagonists, anticholmergics, mast cell inhibitors, antihistamines, antiinflammatoπes, antineoplastics, anesthεtics, anti tuberculars, imaging agents, cardiovascular agents, enzymes, steroids, genetic mateπai, viral vectors, antisεnsε agεnts, proteins, peptidεs and combinations thereof. Particularly preferred bioactive agents comprise compounds which are to be administered systemically (i.e. to the systemic circulation of a patient) such as peptides, proteins or polynucleotides. As will be disclosed in more detail below, the bioactive agent may be incorporated, blεndεd in, coatεd on or othεrwisε associated with the perforated microstructure. In other embodiments, the bioactive agent may be associated with the disperse phase (e.g , aquεous phasε) of a reverse emulsion. Whatever form of stabilized dispersion is employed, the present invention provides methods for the pulmonary delivery of one or more bioactive agents compπsing the steps of: providing a stabilized respiratory dispersion compπsing one or more bioactive agents wherein the respiratory dispersion compπsεs a fluorochemical continuous phase; nebulizing said respiratory dispersion with a nebulizer to provide an aerosolized mεdicamεπt; and admimstεπng a thεrapeutically effective amount of said aerosolized mεdicamεnt to at lεast a portion of the pulmonary passagεs of a patient in need thereof.

When the stabilized dispersion compnses a reversε emulsion, the bioactive agent prεfεrably will bε substantially associatεd with the dispersεd droplets. With respect to particulate dispersions, the selεcted bioactive agent, or agents, may be used as the sole structural component of thε particulates or perforated microstructures. Conversεly, the particulates, or perforated microstructures, may comprise one or more components (i ε. structural matεπals, surfactants, excipients, etc ) in addition to thε incorporated bioactive agents In particularly preferred εmbodimεnts, the suspended particulates or perforated microstructures will comprise relatively high concentrations of surfactant (greater than about 10% w/w) along with the incorporated bioactive agent(s) Finally, it should be appreciated that the particulate or pεrforated microstructure may be coated, linked or otherwise associated with the bioactive agent in a non integral manner. Whatever configuration is selected, it will be appreciated that the associated bioactive agent may be used in its natural form or as onε or more salts known in thε art

In addition to reverse emulsions and suspensions of perforated microstructures, it must be emphasized that the present invention provides for the nebulization and pulmonary delivery of relatively stable particulate dispersions Those skilled in the art will appreciate that, due to other physiochemical characteristics, the morphology of incorporated particulates may vary without destabilizing the dispersion As such, stabilized dispersions may bε formed with compatible particulates even if they exhibit relatively low porosity, or are substantially solid. That is, while particularly preferred embodiments of the present invention will compnse perforated microstructures or microspheres, acceptablε dispersions may be formed using relatively low porosity particulates such as naπocrystals, or micronized drugs. In this respect, such embodiments are spεcifically contemplated as being within thε scopε of the present invention

The stabilized dispersions of the invention may optionally compnse one or more additives to further enhance stability or increase biocompatibility For εxamplε, vaπous surfactants, co solvεnts, osmotic agεnts, stabilizers chelators buffers, viscosity modulators, solubility modifiers and salts can be associated with the pεrforated microstructure, suspension medium, or both The use of such additives will be understood to those of ordinary skill in thε art and, the specific quantities, ratios, and types of agents can be detεrmined empirically without undue expeπmentation

Other objects, features and advantages of the present invention will bε apparent to those skilled in the art from a consideration of the following detailed descπption of preferred exemplary embodiments thεreof

Brief Descnotion of the Drawinos

Figs 1 A 1 to 1 F2 illustrate changes in particle morphology as a function of variation in the ratio of fluorocarbon blowing agent to phospholipid (PFC/PC) present in thε spray dry feed The micrographs, produced using scanning εlεctron microscopy and transmission electron microscopy techniques, show that in the absence of FCs, or at low PFC/PC ratios, the resulting spray dried microstructures comprising gentamicin sulfate arε neither particularly hollow nor porous Conversely, at high PFC/PC ratios, the particles contain numerous pores and are substantially hollow with thin walls.

Fig. 2 is a scanning electron microscopy image of pεrforatεd microstructures comprising cromolyn sodium illustrating a preferred hollow/porous morphology

Fig 3 presents results of in vitro Andersεn cascade impactor studies comparing the same hollow porous cromolyn sodium formulation delivered via MDI m HFA 134a, or from a long chain fluorocarbon (perfluorooctyl ethane) via nebulization Nebulized particles are observed to deposit onto later stages in the impactor corresponding to improved systemic delivery in vivo. Detailed Descnotion Preferred Embodiments

While the present invention may be embodied in many different forms, disclosed herein are specific illustrative embodimεnts thereof that εxεmphfy the principles of thε invention It should bε εmphasizεd that, thε present invention is not limited to the specific embodiments illustrated. As set forth above, the present invention provides systems, methods and compositions that allow for the formation and administration of stabilized suspensions or dispersions, having a nonaqeous continuous phase, that may advantageously be used for the pulmonary delivery of bioactive agents in conjunction with a nebulizer In this regard, it will be appreciated that the stabilized dispersions may comprise any colloidal system, including, reverse emulsions, microemulsions or particulate (i e non liquid particles) dispersions that may be nebulized to effεctively deliver a bioactive agent to the pulmonary air passages of a patient. Particularly preferred embodiments comprise stabilized dispersions incorporating a liquid fluorochemical continuous phase or suspension mεdium In any event, the stabilized dispersion will preferably be administered to the pulmonary air passages of a patiεnt using a nebulizer (e g a single bolus type nebulizer)

Traditional pnor art nebulizer preparations typically comprise aqueous solutions of the selected pharmaceutical compound With such pnor art nebulizer preparations, it has long beεn established that corruption of the incorporated therapeutic compound can severely reduce efficacy For example, with conventional aqueous multi dose nebulizer preparations, bacterial contamination is a constant problem In addition, the solubilizεd mεdicament may precipitate out, or degrade over time, adversεly affecting the delivery profile. This is particularly true of larger, more labile biopolymers such as enzymes or other types of proteins. Precipitation of the incorporated bioactive agent may lead to particle growth that results in a substantial reduction in lung penetration and a corresponding decrease in bioavailability. Such dosing incongruities markedly decreasε the effectiveness of any treatment

The present invention overcomes these and other difficulties by providing stabilized dispersions with a nonaqueous continuous phase that preferably comprises a fluorinated compound (i e a fluorochemical fluorocarbon or perfluorocarbon). Particulariy preferred embodiments of the present invention comprise fluorochemicals that are liquid at room temperature. As indicated abovε, the usε of such compounds, whether as a continuous phase or, as a suspension medium, provides several advantages over prior art liquid inhalation preparations In this regard, it is well established that many fluorochemicals have a proven history of safety and biocompatibility in the lung Further, in contrast to aqueous solutions, fluorochemicals do not negatively impact gas exchange following pulmonary administration To the contrary, they may actually be able to improve gas εxchangε and, due to their unique wettability characteristics, are able to carry an aerosolized stream of particles deeper into the lung, thereby improving systemic delivery of the desired pharmaceutical compound In addition, the relatively non reactive nature of fluorochemicals acts to retard any degradation of an incorporated bioactive agent Finally, many fluorochemicals are also bacteπostatic thereby decreasing the potential for microbial growth in compatible nebulizer devices As previously indicated, the present invention may comprise any one of a number of colloidal systems including, but not limited to, reverse emulsions, microemulsions and particulate dispersions. For the purposes of the instant application the terms shall be used in accordance with their common meanings unless otherwise dictated by contextual constraints. Thus, those skilled in the art will appreciate that emulsions (whether micro, or reverse iwater-in oil!) will compnse a dispersion of liquid particulates in a liquid continuous phasε. Conversely, a paniculate suspension or dispersion shall, as used herein, be held to compnse a distribution of non liquid particles in a liquid continuous phase or suspension medium.

While inhalation preparations compatible with thε present invention may comprise any colloidal system that is capable of nebulization or aerosohzation the following discussion, for the purpose of explanation, will largely be directed to particularly preferred embodiments of the present invention comprising stabilized particulate dispersions. It should be emphasized that, the scope and content of the present invention is not limited to these specific illustrative embodiments and, in particular, is not limited to those embodiments comprising particulate dispersions. While such dispersions are particularly effective in terms of stability and pulmonary distribution, nebulized reverse emulsions may also provide for the efficient pulmonary delivery of bioactive compounds. As such, their use is specifically contemplated as being within the scope of the presεnt invention

With regard to particulate dispersions, the enhanced stability provided by the suspεπsions of the present invention may be achieved by lowering thε van der Waals attractive forces between the suspended particles, and by reducing the differences in density between the suspension medium and the particles. In accordance with thε teachings herεin, thε increases in suspension stability may be imparted by engineering perforated microstructures that are then dispersed in a compatible suspension medium. In this respect, the pεrforatεd microstructures comprise pores, voids, hollows, defεcts or othεr interstitial spaces that allow the fluid suspεnsion medium to freely permeate or perfuse the particulate boundary Particularly preferred embodiments comprise perforated microstructures that are both hollow and porous, almost honeycombed or foam like in appearance In especially preferred embodiments the perforated microstructures comprise hollow, porous spray dried microspheres. When perforated microstructures are placed in the suspension medium, the suspension mεdium is ablε to permεate the particles, thereby creating a "homodispersion", wherein both the continuous and dispersεd phases are essentially indistinguishable Since the definεd or "virtual" particles (i.e comprising the volume circumscribed by the microstructure matrix) are made up almost entirely of the medium in which they are suspended, the forces driving particle aggregation (flocculation) are minimized. Additionally, thε differences in density between the defined or virtual particles and the continuous phasε arε minimized by having thε microstructures filled with thε medium, thereby effectively slowing particle creaming or sedimentation As such the stabilized suspensions of the present invention are particularly compatible with inhalation therapies and may be usεd in conjunction with metered dose inhalers (MDIs), dry powder inhalers, and nebulizers. More specifically, thε particulate suspensions of the present invention may be designed to decrease the attractive forces between particles. The principal forces driving flocculation in nonaqueous media are van der Waals attractive forces. Van der Waals forces are quantum mechanical in origin, and can be visualized as attractions between fluctuating dipoles (i.e. induced dipole-mduced dipole interactions). Dispersion forces are extremεly short rangε and scale as thε sixth power of the distance betweεn atoms. When two macroscopic bodies approach one another, the dispersion attractions betweεn the atoms sum up. The resulting force is of considerably longer range, and depends on the geometry of the interacting bodies.

More specifically, for two spherical particles, the magnitude of the van der Waals potential, V _A , can be approximated by _{v =} ~ O ^R < R ι where A_eff is the effεctivε Hamakεr constant which accounts for 6 H ₀ ( Λ , + Λ ₂ ) the nature of the particles and the medium, H₀ is the distance between particles, and R, and R₂ are the radii of spherical particles 1 and 2 The effective Hamaker constant is proportional to the difference in the polanzabilities of the dispersεd particles and the suspension mεdium. =

- / Α _PART ) ' - where

ASM ^and ^PART ^{are tne} Hamaker constants for the suspension mεdium and the particles, respectively As thε suspended particles and the dispersion mεdium bεcomε similar in naturε, A_M and A_PART bεcomε closer in magnitude, and A_eff and V_A become smaller. That is, by reducing the diffεrεnces betwεεn the Hamaker constant associated with suspension medium and the Hamaker constant associated with the dispersed particles, the effective Hamaker constant (and corresponding van der Waals attractive forces) may be reduced.

One way to minimize the differences in the Hamaker constants is to create a "homodispersion", that is make both the continuous and dispersed phases essentially indistinguishable as discussed above In addition to exploiting the morphology of the particles to reduce the effective Hamaker constant, the componεπts of thε structural matrix (defining the perforated microstructures) will prεfεrably bε chosεn so as to exhibit a Hamaker constant relatively close to that of the selected suspension medium. In this respect, one may use the actual values of the Hamakεr constants of thε suspension mεdium and thε particulate components to detεrmine the compatibility of the dispersion ingredients and to provide a good indication as to the stability of thε preparation. Alternatively, one could select relatively compatible pεrforated microstructure components and suspension mediums using readily discernible characteristic physical values that coincide with measurable Hamaker constants

In this respect, it has been found that the refractive index values of many compounds tend to scale with thε corresponding Hamaker constant Accordingly, easily measurable refractive index values may be used to provide a fairly good indication as to which combination of suspension medium and particle excipients will provide a dispersion having a relatively low effective Hamaker constant and associated stability It will be apprεciatεd that, since refractive indices of compounds are widεly available or easily derived, the use of such values allows for the formation of stabilized dispersions in accordance with the present invention without undue experimentation. For the purpose of illustration only, the rεfractive indices of sevεral compounds compatible with the disclosed dispersions are provided in Table I immediately below:

Table I

Compound Rεfractive Index

HFA-134a 1.172

HFA-227 1.223

CFC-12 1.287

CFC-114 1.288

PFOB 1.305

Mannitol 1.333

Ethanol 1.361 n-octane 1.397

DMPC 1.43

Pluronic F-68 1.43

Sucrosε 1.538

Hydroxyethylstarch 1.54

Sodium chloride 1.544

Consistent with thε compatible dispersion components set forth above, those skilled in the art will appreciate that the formation of dispersions whεrεin thε components have a refractive index differential of less than about 0.5 is prεfεrred. That is, the refractive index of the suspension mεdium will prεferably be within about

0.5 of thε refractive index associated with the suspended particles or perforated microstructures. It will further be appreciated that, the refractive index of the suspεnsion mεdium and thε particles may be measurεd directly or approximated using the refractive indices of the major component in each respective phase. For the particles or perforatεd microstructures, the major component may be determinεd on a weight percent basis. For the suspension medium, the major component will typically be derived on a volume percentage basis. In selected embodiments of the prεsεnt invention, the refractivε indεx differential value will prefεrably be less than about 0.45, about 0.4, about 0.35 or even less than about 0.3. Given that lower refractivε index differentials imply greater dispersion stability, particularly prefεrrεd εmbodimεnts comprise indεx differentials of less than about 0.28, about 0.25, about 0.2, about 0.15 or even less than about 0.1. It is submitted that a skillεd artisan will be able to dεtεrmine which dispersion components are particularly compatible without undue experimentation given the instant disclosure. The ultimate choice of preferred components will also be influenced by other factors, including biocompatibility, regulatory status, ease of manufacture and cost. In contrast to prior art attempts to provide stabilized suspensions which require surfactants that are soluble in the suspension medium, the present invention may provide stabilized dispersions, at least in part, by immobilizing the bioactive agent(s) within thε structural matrix of thε hollow, porous microstructures Accordingly, preferred excipients useful in thε present invention are substantially insoluble in thε suspension medium Under such conditions, even surfactants like, for example, lecithin cannot be considered to have surfactant properties in thε present invention since surfactant pεrformaπcε requires the amphiphile to be rεasonably soluble in the suspension mεdium The use of insoluble excipients also reduces thε potential for particle growth by Ostwald ripening.

As discussed above, thε minimization of density differences betwεεn the particles and the continuous phase may be improved by the pεrforated and/or hollow nature of incorporated microstructures, such that the suspension medium constitutes most of thε particle volume As used herein, the term "particle volume" corresponds to the volume of suspension medium that would be displaced by the incorporated hollow/porous particles if they werε solid, i e the volume defined by the particle boundary For thε purposεs of explanation these fluid filled particulate volumεs may be referred to as "virtual particles " Preferably, thε average volume of the bioactive agent and/or excipient shell or matrix (i e. thε volumε of mεdium actually displaced by the perforated microstructure) comprises lεss than 70% of the average particle volume (or less than 70% of the virtual particle). More preferably, the volume of the microparticulate matrix comprises lεss than about 50%, 40%, 30% or εvεn 20% of the averagε particle volume. Even more preferably, the average volume of the shell/matrix comprises lεss than about 10%, 5% or 3% of thε average particle volume Those skilled in the art will appreciate that such matrix, or shell volumes typically contribute little to the virtual particle density that is overwhelmingly dictated by thε suspεnsion mεdium found thεrein Of course, in selected embodiments the excipients or bioactive agents used to form the perforated microstructure may be chosen so the density of the resulting matrix or shell approximates the density of the surrounding suspεnsion medium

It will be appreciated that, the usε of such microstructures will allow the apparent density of the virtual particles to approach that of thε suspεnsion mεdium Moreover, as previously discussed, thε componεnts of thε microparticulate matrix are prefεrably selected, as much as possible given other considerations, to approximate the density of suspension medium Accordingly, in preferred embodiments of thε present invention thε virtual particles and the suspension medium will have a density differential of less than about 0 6 g/cm³. That is, the mean density of the virtual particles (as definεd by thε matrix boundary) will bε within approximately 0 6 g/cm³ of the suspension medium. More prefεrably, the mean density of the virtual particles will be within 0.5, 0.4, 0.3 or

0 2 g/cm^J of the sεlεctεd suspεnsion medium In even more preferable embodiments the density differential will be less than about 0.1 , 0.05, 0.01 , or even less than 0.005 g/cm".

u- In addition to the aforemεntioned advantages, thε usε of hollow, porous particles allows for the formation of free-flowing dispersions comprising much higher volumε fractions of particles in suspension. It should be apprεciated that, the formulation of prior art dispersions at volume fractions approaching close packing generally results in dramatic increases in dispersion viscoelastic behavior Rheological behavior of this type is not appropriate for inhalation applications. Those skilled in the art will appreciate that, the volumε fraction of the particles may be defined as thε ratio of thε apparent volume of the particles (i e. the particle volume) to the total volume of the system. Each system has a maximum volume fraction or packing fraction For example, particles in a simple cubic arrangement reach a maximum packing fraction of 0.52, while those in a face centered cubic/hexagonal close packed configuration reach a maximum packing fraction of approximately 0 74 For non spherical particles or polydisperse systems, the derived values are different. Accordingly, the maximum packing fraction is often considered to be an empirical parametεr for a given system.

Here, it was surprisingly found that, the use of porous structures in the present invention did not introduce undesirable viscoelastic behavior even at high volume fractions approaching close packing To the contrary, they remain as free flowing, low viscosity suspensions having little or no yield stress when compared with analogous suspensions comprising solid particulates The low viscosity of disclosεd prεferred suspεnsions is thought to be due, at least in large part, to the relatively low van der Waals attraction between the fluid filled hollow, porous particles As such, in selected embodimεnts the volume fraction of the disclosεd dispεrsions is greater than approximately 0.3. Other embodiments may have packing values on the order of 0 3 to about 0.5 or, on the order of 0 5 to about 0 8, with the higher values approaching a close packing condition Moreover as particle sedimentation tends to naturally decrease when the volume fraction approaches close packing, the formation of relatively concentratεd dispεrsions may further increase formulation stability

Although the methods and compositions of thε prεsεnt invention may be used to form relatively concentratεd suspensions, the stabilizing factors work equally well at much lower packing volumes and, such dispersions are contemplated as being within the scope of thε instant disclosurε In this rεgard, it will be appreciated that dispersions comprising low volume fractions are extremεly difficult to stabilize using prior art techniquεs. Conversεly, dispersions incorporating perforated microstructures comprising a bioactive agent as described hεrein are particularly stable εvεn at low volume fractions Accordingly, the prεsεnt invention allows for stabihzed dispersions, and particularly respiratory dispersions, to be formed and used, at volume fractions less than 0.3 In somε preferred embodimεnts, the volume fraction is approximately 0 0001 0 3, or more preferably 0.001 0 01. Yet other prεferred embodiments comprise stabilized suspεnsions having volumε fractions from approximately 0 01 to approximately 0 1

In other preferred embodiments, perforated microstructures may be used to stabilize dilute suspensions of micronized bioactive agεnts In such embodiments the perforated microstructures mav be added to increase the volume fraction of particles in the suspεnsion, thereby increasing suspension stability with respect to creaming or sedimentation. Further, in these embodiments, the incorporated microstructures may also act in preventing close approach (aggregation) of micronized drug particles. It should bε appreciated that, thε perforated microstructures incorporated in such embodiments do not necessarily comprise a bioactive agent. Rather, they may bε formεd exclusively of various excipients, including surfactants.

Of course, it will also be appreciated that thε stabilized dispersions of the present invention may comprise relatively solid or non perforated particulates without the addition of perforatεd microstructures. That is, depending on the size, composition and density of the suspended microparticulates, as well as the selection of suspεnsion mεdium, effective particulate dispersions for nebulization may bε formed using relatively non porous or micronized particulates. In a preferred embodiment, the suspεnded particulates may comprise πanocrystals such as those disclosεd in U S. Pat. No 5,667,809 which is incorporated herein by reference. As with embodimεπts comprising perforated microstructures, such preparations will preferably comprise a fluorochemical suspension medium Accordingly, in a broad sεnsε, the prεsεnt invention provides for the formation and pulmonary administration of stabilized dispersions comprising relatively non porous particulates (e.g. micronized particles), porous particulates (I e. hollow porous microspheres or perforatεd microstructures) and combinations thereof

While the stabilized dispersions may comprise particulates exhibiting various morphologies, particularly preferred εmbodimεnts of the presεnt invention comprise a plurality of perforated microstructures or microparticulates that are dispersed, or suspended in the suspension medium. In such embodiments, the perforatεd microstructures compose a structural matrix that exhibits, defines or composes voids, pores, dεfεcts, hollows, spaces, interstitial spaces, apertures, perforations or holes that allows thε surrounding suspension medium to freely permεatε, fill or pervade the microstructure The absolute shape (as opposed to thε morphology) of thε perforated microstructure is generally not critical and any overall configuration that provides the desired stabilization characteristics is contemplated as being within the scope of thε invention Accordingly, while preferred embodiments incorporating perforated microstructures can comprise approximately microsplieπcal shapes, collapsed, deformεd or fractured particulates are also compatible. With that caveat, it will be apprεciated that particularly prεferred embodiments of the invention compose spray dned hollow, porous microsphεres.

In order to maximizε dispersion stability and optimize distnbution upon administration, the mean geometric particle size of the perforatεd microstructures is preferably about 0.5 50 m, more preferably 1 30 m. It will bε appreciated that, large particles (i.e. greater than 50 m) should not be used as large particles may tεnd to aggregatε or, separata from the suspension and not be effεctively nebulized. In especially preferred embodiments, the mean gεomεtπc particle size (or diameter) of the perforated microstructures is lεss than 20 m or less than 10 m. More preferably, the mean geometπc diameter is less than about 5 In especially preferred εmbodimεnts, thε perforatεd microstructures will compπsε a powdεr of dry, hollow, porous microsphεπcal shells of approximatεly 1 to 10 m diameter, with shell thicknesses of approximately 0.1 m to approximately 0.5 m. It is a particular advantage of the presεπt invention that, the particulate concentration of the dispersions and structural matπx components can be adjusted to optimize thε delivery characteπstics of the selected particle size.

As indicated throughout the instant specification, the dispersions of the present invention are preferably stabilized. In a broad sense, the term "stabilized dispersion" will be held to mean any dispersion that resists aggregation, flocculation or creaming to the extent required to provide for the effεctive delivery of a bioactive agεnt. While thosε skilled in the art will appreciate that there are several methods that may be used to assess the stability of a given dispersion, a preferred method for thε purposes of the present invention comprises determination of creaming or sedimentation timε. In this rεgard, thε creaming time shall be defined as the timε for the suspεndεd drug particulates to cream to 1 \2 the volume of thε suspension medium. Similarly, thε sedimentation time may be defined as the time it takes for the particulates to sediment in 1/2 the volume of the liquid mεdium Onε relatively simple way to determine the creaming time of a preparation is to provide the particulate suspension in a sealed glass vial. Thε vials are agitated or shaken to provide relatively homogeneous dispersions which are then set aside and observεd using appropπate instrumentation or by visual inspection. The time necessary for the suspεndεd particulates to cream to 1 /2 thε volumε of the suspension medium (i.e., to rise to thε top half of thε suspεnsion mεdium), or to sεdimεnt within 1 /2 thε volume (i.e., to settle in the bottom 1 /2 of the medium), is then noted. Suspεnsioπ formulations having a creaming time greater than 1 minute are preferred and indicate suitable stability. More preferably, the stabilized dispersions compnse creaming times of greater than about 2, 5, 10, 15, 20 or 30 minutes. In particularly prefεrred embodimεπts, the stabilized dispersions exhibit creaming times of greater than about 1, 1 5, 2, 2.5, 3, 4 or even 5 hours Substantially equivalent periods for sedimentation times are indicative of compatible dispersions.

With respect to the preparations of the present invention, the porosity of incorporated microstructures may contribute significantly to establishing dispersion stability. In this respect, the mean porosity of the perforatεd microstructures may be determined through εlεctron microscopy coupled with modern imaging techniques More specifically, electron micrographs of representative samples of the pεrforated microstructures may be obtained and digitally analyzed to quantify the porosity of the preparation. Such methodology is well known in thε art and, may bε undertaken without undue experimentation.

For the purposes of thε presεnt invention, thε mεan porosity (i.e. the percentage of the particle surface area that is open to the interior and/or a central void) of the perforated microstructures may range from approximately 0.5% to approximately 80% In more preferred embodiments, the mean porosity will rangε from approximately 2% to approximatεly 40%. Based on selected production parameters, the mean porosity may bε greater than approximately,

2%, 5%, 10%, 15%, 20%, 25% or 30% of the microstructure surface area In other embodimεnts, the mean porosity of the microstructures may be greater than about 40%, 50%, 60%, 70% or even 80%. As to the pores themselves, they typically range in size from about 5 nm to about 400 nm, with mean pore sizes prεfεrably in the range of from about 20 nm to about 200 nm In particularly preferred embodimεnts the mean pore size will be in the rangε of from about 50 nm to about 100 nm. As may be seen in Figs. 1 A1 to 1 F2, and discussed in more detail below, it is a significant advantage of the present invention that the pore size, and porosity, may be closely controlled by careful selection of the incorporated components and production parametεrs. Along with thε gεometπc configuration, thε pεrforatεd or porous and/or hollow dεsign of microstructurεs can also play an important role in thε resulting aerosol properties during nebulization. In this respect, the pεrforated structure, and relatively high surface area of thε dispersed microparticles, enables them to be earned along in the aerosol cloud during inhalation with greater ease and, for longer distances, than non pεrforatεd particles of comparable size. Bεcausε of thεir high porosity, thε density of the particles is significantly less than 1 0 g/cm³, typically less than 0.5 g/cm³, more often on the order of 0.1 g/cm³, and as low as 0.01 g/cm³. Unlike the geometric particle size, thε aerodynamic particle size, d_aer , of thε perforated microstructures depεnds substantially on thε particle density, p : d_aer = d p , where d is the geometric diameter For a particle density of 0 1 g/cm³, d _aer will be roughly three times smaller than d , leading to increased particle deposition into the peripheral regions of the lung and correspondingly less deposition in the throat. In this rεgard, thε mεan aεrodyπamic diamεtεr of thε perforated microstructurεs is prεfεrably lεss than about 5 μm, morε preferably less than about 3 μm, and, in particularly preferred embodiments, lεss than about 2 μm. Such particlε distributions will act to increase thε dεep lung deposition of the administered agent.

As will be shown subsεquently in the Examples, the particle size distribution of the aerosol formulations of the present invention are measurablε by conventional techniques such as cascade impaction, or by timε of flight analytical mεthods. Determination of the emitted dose in nebulized inhalations was done according to the proposed U S Pharmacopeia method [Pharmacopeia/ Previews, 22( 1996) 3065) which is incorporated herein by reference These and relatεd techniques enable the 'fine particle fraction of the nebulized aerosol, which corresponds to those particulates that are likely to effectively deposited in thε lung, to bε calculated As used herein, the phrase "fine particle fraction" refεrs to thε pεrceπtage of the total amount of active medicament delivered per actuation from the mouthpiece onto plates 2 7 of an 8 stage Andersen cascade impactor Based on such measurements, the formulations of the presεnt invention will preferably have a fine particle fraction for local airway delivery of approximately 20% or more by wεight of the pεrforatεd microstructurεs (w/w) Morε preferably, they will exhibit a fine particle fraction of from about 25% to 80% w/w, and evεπ more preferably from about 30 to 70% wlw In sεlεctεd εmbodiments thε prεsεnt invention will prεfεrabiy comprise a fine particle fraction of greater than about 30%, 40%, 50%, 60%, 70% or 80% by weight For systemic delivery, the fine particle fraction will preferably be greater than 80% by wεight, more preferably, grεatεr than 90% by wεight Whatever configuration and/or size distπbution is ultimately selected for the incorporated particulate (whether a perforated microstructure or relatively solid non porous particulate), the composition thereof may compose any one of a number of biocompatible materials With rεgard to pεrforatεd microstructurεs, it will be appreciated that, as used herein, the terms "structural matπx" or "microstructure matrix" are equivalent and shall be held to mean any solid material forming the pεrforatεd microstructurεs which define a plurality of voids, apertures, hollows, defεcts, porεs, holεs, fissures, etc. that promote the formation of stabilized dispersions as explained above. The structural matπx may bε soluble or insoluble in an aqueous environment. In preferred embodimεnts thε pεrforatεd microstructure defined by the structural matπx compnsεs a spray dπεd hollow porous microsphεrε incorporating at lεast onε surfactant. For other selected embodiments, the particulate material may be coatεd onε or more times with polymers, surfactants or other compounds which aid suspension.

More generally, particulates useful in the stabilized dispεrsions of the present invention may bε formεd of any biocompatible matenal that is relatively stable and preferably insoluble with respect to the selected suspension mεdium. While a wide variety of materials may bε usεd to form thε particles, in particularly prεfεrrεd εmbodimεnts, the particles (or structural matrix) is associated with, or comprises, a surfactant such as phospholipid or fluorinated surfactant. Although not required, incorporation of a compatible surfactant can improve the stability of the respiratory dispersions, increase pulmonary deposition and facilitate the preparation of the suspension. Moreover, by alteππg the components, the density of the particle or structural matπx may bε adjusted to approximate the density of thε surrounding medium and further stabilize the dispersion, finally, as will be discussed in further detail below, perforated microstructurεs preferably compnse at least one bioactive agent As set forth above, the relatively non porous particles or perforated microstructures of thε present invention, may optionally be associated with, or compnse, one or more surfactants Moreovεr, miscible surfactants may optionally be combined with the suspεnsion mεdium liquid phasε. It will be appreciated by those skilled in thε art that, the use of surfactants, while not nεcεssary to practice the instant invention, may further increase dispersion stability, simplify formulation procedures or increase bioavailability upon administration. Of course combinations of surfactants, including the use of one or more in thε liquid phasε and onε or morε associated with thε pεrforatεd microstructures are contemplated as being within the scope of the invention. By "associated with or comprise" it is meant that the particle or perforatεd microstructure may incorporate, adsorb, absorb, be coated with or be formed by thε surfactant

In a broad sense, surfactants suitable for use in the presεnt invention include any compound or composition that aids in the formation and maintenance of the stabilized respiratory dispersions by forming a layer at the interface between the particle and thε suspεnsion mεdium. The surfactant may compnse a single compound or any combination of compounds, such as in the case of co surfactants Particularly prefεrrεd surfactants are substantially insoluble in the medium, nonfluonnated, and selected from the group consisting of saturated and unsaturated lipids, nonionic detergents, nonionic block copolymers, ionic surfactants, and combinations of such agεnts It should be emphasized that, in addition to the aforementioned surfactants, suitable (i e biocompatible) fluoπnated surfactants are compatible with the teachings herein and may be used to provide the desired stabilized preparations

Lipids, including phospholipids, from both natural and synthetic sources are particularly compatible with the present invention and may be used in varying concentrations to form the particle or structural matπx.

Generally compatible lipids comprise those that have a gel to liquid crystal phasε transition greater than about 40°C Preferably, the incorporated lipids are relatively long chain (i.e. C,₆ C ) saturated lipids and more preferably compnse phospholipids. Exemplary phospholipids useful in the disclosed stabilized preparations comprise egg phosphatidylcholme, dilauroylphosphatidylcholine, dioleylphosphatidylchohne, dipalmitoylphosphatidyl choline, disteroylphosphatidylcholine, short-chain phosphatidylcholines, phosphatidγlethanolamiπe, dioieylphosphatidylethanolamine, phosphatidylseπne, phosphatidylglycerol, phosphatidylinositol, glycolipids, ganglioside GM1 , sphingomyelin, phosphatidic acid, cardiolipin; lipids beanng polymer chains such as polyethylene glycol, chitin, hyaluronic acid, or polyvinylpyrro done; lipids bearing sulfonated mono , di , and polysacchandes; fatty acids such as palmitic acid, steaπc acid, and oleic acid, cholesterol, cholesterol esters, and cholesterol hemisuccinate. Due to their excellent biocompatibility charactenstics, phospholipids and combinations of phospholipids and poloxamers are particularly suitable for use in the stabilized dispersions disclosed herein.

Compatible nonionic detergents comprise, sorbitan esters including sorbitan tnoleate (Span 85), sorbitan sesquioleate, sorbitan monooleate, sorbitan monolaurate, polyoxyethylene (20) sorbitan monolaurate, and polyoxyethylene (201 sorbitan monooleate, oleyl polyoxyethylene (21 ether, stearyl polyoxyethylene (2) ether, lauryl polyoxyethylene (4) ether, glycerol esters, and sucrose esters. Other suitable nonionic detergents can be easily identified using McCutcheon's Emulsifiers and Detergents (McPublishmg Co , Glen Rock, New Jersey) which is incorporated herein in its entirety. Preferred block copolymers include diblock and tπblock copolymers of polyoxyethylene and polyoxypropylene, including poloxamer 188 (Pluromc " F 68), poloxamer 407 (Pluronic " F 127), and poloxamer 338 Ionic surfactants such as sodium sulfosucciπate, and fatty acid soaps may also be utilized. In preferred embodiments the microstructures may co pnse oleic acid or its alkali salt.

In addition to the aforementioned surfactants, cation'c surfactants or lipids are preferred especially in the case of delivery or RNA or DNA Examples of suitable cationi- lipids include- cetylpyπdinium chloride, DOTMA, N [1 (2,3 dioleyloxylpropyl] N,N,N tπmβthylammonium chlonde, DOTAP, 1,2 dioleyioxy 3

(tπmethylammonιo)propane; and DOTB, 1,2 dioleyl 3 (4' tπmethyiammonio) butanoyl sn glycerol Polycationic ammo acids such as polylysme, and polyargiπiπe are also contemplated.

Those skilled in the art will further appreciate that, a wide range of surfactants, including those not listed above, may optionally be used in conjunction with thε present invention. Moreover, the optimum surfactant, or combination thereof, for a given application can readily be detεrmiπεd by εmpiπcal studiεs that do not require undue experimentation. It will further be appreciated that, the preferred insolubility of any incorporated surfactant in the suspεnsion medium will dramatically decrease the associated surface activity As such, it is arguable as to whether these materials have surfactant-like character prior to contracting an aqueous bioactive surface (e g. the aqueous hypophasε in thε lung). Finally, as discussed in more detail below, surfactants comprising the porous particles may also be useful in the formation of precursor oil-in water emulsions (i.e. spray drying feed stock) used during processing to form the structural matrix or bioactive particulate.

Unlike pnor art formulations, it has surpπsiπgly beεn found that thε incorporation of relatively high levels of surfactants (i.e. phospholipids) may be usεd to incrεasε thε stability of thε disclosεd dispersions. That is, on a weight to weight basis, the structural matπx of the perforated microstructures may comprise relatively high levels of surfactant. In this regard, the perforated microstructures will prefεrably compnse greater than about 1 %, 5%, 10%, 15%, 18%, or evεn 20% w/w surfactant. More prefεrably, the perforated microstructures will comprise greater than about 25%, 30%, 35%, 40%, 45%, or 50% w/w surfactant. Still other εxεmplary εmbodimεnts will comprise perforatεd microstructurεs wherein the surfactant or surfactants are present at greater than about 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or even 95% w/w In sεlected embodimεnts thε pεrforated microstructures will compose essentially 100% w/w of a surfactant such as a phospholipid. Those skilled in the art will appreciate that, in such cases, the balance of the structural matπx (where applicable) will likely compnse a bioactive agent(s) or non surface active excιpιent(s) or addιtιvε(s).

As previously indicated, stabilized dispersions comprising perforated microstructures merely represent a preferred embodimεnt of thε prεsεnt invεntion Accordingly, while such surfactant levels are preferably empioyεd in perforated microstructures, equivalent surfactant levels may also be used to provide stabilized systems composing relatively nonporous, or substantially solid, particulates That is, while preferred embodimεnts will compπsε pεrforatεd microstructures or microspheres associated with high levels of surfactant, acceptable dispersions may be formed using relatively low or non porous particulates (ε g micronized particulates) of the samε surfactant concεntration In this respect such embodimεnts are specifically contemplated as being within the scopε of thε present invention. In other preferred embodiments, relatively non porous particles or the structural matπx defining thε pεrforatεd microstructurεs optionally compπsεs synthetic or natural polymers or combinations thereof. In this respect useful polymers compnse polylactides, polylactide glycohdes, cyclodextnns, polyacrylatεs, mεthylcellulose, carboxymethylcellulose, polyvinyl alcohols, polyanhydπdεs, polylactons, polyvinyl pyrrolidones, polysacchandes (dextrans, starches, chitin, chitosan, etc.), hyaluronic acid, proteins, (albumin, collagen, gelatin, etc ). Those skilled in the art will appreciate that, by selecting the appropπate polymers, thε delivery profile of the respiratory dispersion may be tailored to optimize the effectiveness of the bioactive agent

In addition to the aforementionεd polymer materials and surfactants, it may be desirable to add other excipients to an inhalation formulation to improve microsphεrε (or non porous particulate) rigidity, drug delivery and deposition, shelf life and patient acceptance. Such optional excipients include, but are not limitεd to: coloring agents, taste masking agents, buffers, hygroscopic agεnts, antioxidants, and chεmical stabilizers. Further, excipients may be incorporated in, or added to, thε particles or particulate matrix to provide structure and form to the perforated microstructures (i.e. microspheres). Such excipients may include, but are not limited to, carbohydrates including monosacchandes, disacchandes and polysacchandes. For εxamplε, monosacchaπdεs such as dεxtrosε (anhydrous and moπohydrate), galactose, mannitol, D manπose, sorbitol, sorbose and the like, disacchandes such as lactose, maltose, sucrose, trehalosε, and thε like; tπsacchaπdεs such as raffmose and the like; and other carbohydrates such as starches (hydroxyethylstarch), cyclodextnns and maltodextnns. Ammo acids are also suitable excipients with glycine preferred Mixtures of carbohydrates and ammo acids are further held to be within the scope of thε present invention. The inclusion of both inorganic (e.g. sodium chloride, calcium chloride), organic salts (e g. sodium citratε, sodium ascorbate, magnesium gluconate, sodium gluconate, tromethamine hydrochloπdεl and buffers is also contemplated. Of course, it will bε appreciated that, the selectεd excipients may bε addεd to thε dispersion as separate particles or perforated microstructures

Yet other prefεrred embodimεnts include non porous particles or pεrforatεd microstructurεs that may compπsε, or may bε coatεd with, charged speciεs that prolong rεsidεncε timε at the point of contact or enhance penεtration through mucosaε. For example, anionic charges are known to favor mucoadhesion while cationic charges may be used to associate the formed microparticulatε with negatively charged bioactive agents such as genetic mateπai. The charges may bε impartεd through thε association or incorporation of polyaπionic or polycatiomc matεπals such as poiyacryltc acids, polyiysinε, polylactic acid and chitosan In addition to, or instead of, the components discussed above, the particles, perforatεd microstructures or aqueous emulsion droplets will preferably comprise at lεast onε bioactivε agεnt As usεd hεrεin, "bioactivε agent" rεfεrs to a substance which is used in connection with an application that is therapeutic or diagnostic in nature, such as in methods for diagnosing the presεπce or absence of a diseasε in a patiεnt and/or in mεthods for treating a disease in a patient. Particularly preferred bioactive agents for use in accordance with the invention include anti allergies, peptides and proteins, bronchodilators and anti inflammatory stεroids for usε in thε trεatmεnt of respiratory disorders such as asthma by inhalation therapy.

It will bε appreciated that, the distributed particles or perforatεd microstructures of the present invention may exclusively compnse one or morε bioactive agεπts (i.ε. 100% w/w). However, in selεcted embodiments the particles or perforatεd microstructures may incorporate much less bioactive agεnt dεpεnding on the activity thereof. Accordingly, for highly active mateπals, the particles may incorporate as little as 0.001 % by weight, although a concentration of greater than about 0 1 % w/w is prefεrred Other embodimεnts of the invention may compnse greater than about 5%, 10%, 15%, 20%, 25%, 30% or, even 40% w/w bioactivε agent. Still morε preferably, the particles or pεrforatεd microstructurεs may compnsε greater than about 50%, 60%, 70%, 75%, 80% or, even 90% w/w bioactivε agεnt. In particularly preferred embodimεnts, the final stabilized respiratory dispersion desirably contains from about 40% 60% w/w, more preferably 50% - 70% w/w, and even more preferably, 60% 90% w/w of bioactive agεnt rεlativε to the weight of thε microparticulate matrix or particulate. The precise amount of bioactive agent incorporated in the stabilized dispersions of the present invention is dependent upon the agεnt of choice, the required dose, and the form of the drug actually used for incorporation Those skilled in the art will appreciate that, such determinations may be made by using well-known pharmacological tεchniquεs, in combination with the teachings of the present invention.

Accordingly, bioactive agεnts that may bε administered in the form of aerosolized mεdicamεnts in conjunction with thε teachings herεiπ include any drug that may be preseπtεd in a form which is subject to pulmonary uptake in physiologically effective amounts In selεctεd εmbodiments (e.g. particulate dispersions), the incorporated agent will preferably be relatively insoluble in the suspension medium. In other embodiments, such as reverse emulsions, the selεctεd agεnt may be substantially soluble in the dispersε phasε Particulariy preferred embodiments compπsing a revεrse emulsion will preferably comprise a hydrophilic bioactive agent.

In any case, compatible bioactive agents may compnse hydrophilic and lipophilic respiratory agents, bronchodilators, antibiotics, antivirals, anti-mflammatones, steroids, antihistaminics, histamiπe antagonists, leukotnene inhibitors or antagonists, anticholmergics, antineoplastics, anesthetics, enzymes, lung surfactants, cardiovascular agεnts, genetic material including DNA and RNA, viral vectors, immuπoactive agents, imaging agents, vaccines, immunosuppressivε agεnts, pεptidεs, protεins and combinations thεrεof. Particularly prεfεrrεd bioactivε agεnts, for local administration using aerosolized medicaments in accordance with thε present invention include, mast cell inhibitors (anti allergies), bronchodilators, and anti inflammatory steroids for usε in thε treatment of respiratory disorders such as asthma by inhalation therapy, for example cromoglycate (e.g. the sodium salt), and albuterol

(e.g. the sulfate salt). For systemic delivery (e.g. for the treatment of autoimmune diseasεs such as diabetes or multiple sclerosis), peptides and protεins are particularly preferred.

Exemplary mεdicamεnts or bioactive agεnts may bε selected from, for example, analgesics, e g. codeine, dihydromorphiπε, εrgotammε, fεntanyl, or morphine; anginal preparations, e.g. diltiazem; mast cell inhibitors, e.g. cromolyn sodium; antunfectivεs, ε g. cεphalospoπns, macrolidεs, quinolines, penicillins, streptomycin, sulphoπamides, tetracyclmes and pentamidiπε, antihistamines, e.g. methapynlεnε, aπti-iπflammatoπes, e.g. fluticasone propionate, bεclomethasone dipropionate, flumsolide budesonidε, tnpεdanε, cortisonε, prεdnisonε, predmsilone, dεxamεthasonε, bεtamethasoπe, or triamcinoloπe acetomde, aπtitussives, ε g. noscapiπe, bronchodilators, e.g. ephεdπne, adrenaline, fenoterol, for otεrol, isoprεnalinε, mεtaprotεrenol, salbutamol, albuterol, salmetercl, tεrbutahne; diuretics, e.g. amilonde, anticholmergics, e.g. φatropium, atropine, or oxitropium, lung surfactants ε g Surfaxm, Exosurf, Survanta; xanthinεs, ε.g aminophyllinε, thεophylline, caffeine; therapeutic proteins and peptides, e.g. DNAse, insulin, glucagon, T cell receptor agonists or antagonists, LHRH, πafarelin, goserεlin, leuprohdε, intεrferon, rhu IL 1 receptor, macrophage activation factors such as lymphokinεs and muramyl dipeptides, opioid peptides and neuropeptidεs such as εnkaphalms, εndorphins, rεnin inhibitors, cholecystokimns, growth hormones, leukotnene inhibitors, α antitrypsin, and the like In addition, bioactivε agεnts that comprise an RNA or DNA sequence, particularly those usεful for gene therapy, genetic vaccination or tolenzatioπ or aπtisεnse applications, may bε incorporated in the disclosed dispersions as described herein. Representative DNA plasmids include pCMVβ (available from Genzyme Corp, Framington, MA) and pCMV β gal (a

CMV promotor linked to thε E coh Lac Z genε, which codεs for thε εnzyme β galactosidase)

With respect to particulate dispersions, thε selεctεd bioactivε agεnt(s) may be associated with, or incorporated in, the particles or perforated microstructures in any form that provides the desired efficacy and is compatible with the chosen production techniques. Similarly, thε incorporated bioactivε agεnt may be associated with the discontinuous phase of a reversε εmulsioπ. As used herein, the terms "associate" or "associating" mean that the structural matnx, perforated microstructure, relatively non porous particle or discontinuous phase may compose, incorporate, adsorb, absorb, bε coatεd with or be formed by the bioactive agent. Where appropriate, the medicamεnts may bε used in the form of salts (e g. alkali mεtal or aminε salts or as acid addition salts), or as εstεrs, or as solvates (hydrates). In this regard, the form of the bioactive agents may be selected to optimize the activity and/or stability of the mεdicamεnt and/or, to minimize the solubility of the medicament in thε suspεnsion medium.

It will further be appreciated that the aerosolized formulations according to the invention may, if desired, contain a combination of two or more active ingredients The agents may be provided in combination in a single species of perforated microstructure or particle or individually in separate species that are combiπεd in the suspension medium or continuous phase For example, two or more bioactive agents may be incorporated in a single feed stock preparation and spray dried to provide a single microstructure speciεs comprising a plurality of mεdicamεnts Conversely, the individual medicamεnts could bε addεd to sεparate stocks and spray dried separately to provide a plurality of microstructure speciεs with different compositions. These individual species could be addεd to thε mεdium in any desired proportion and placed in inhalation delivery systems as described below. Further, as briefly mentioned above, the perforated microstructurεs (with or without an associated medicament) may be combined with one or more conventionally micronized bioactive agents to provide the desired dispersion stability.

Basεd on thε foregoing, it will be appreciated by those skilled in the art that a wide vaπεty of bioactivε agents may be incorporated in the disclosed stabilized dispersions. Accordingly, the list of prεferred bioactive agents above is exεmplary only and not intended to be limiting It will also be appreciated by those skilled in the art that, the proper amount of bioactive agent and the timing of thε dosagεs may be determiπεd for the formulations in accordance with already existing information and without undue εxpεπmεntation As sεεπ from thε passages above, various components may be associated with, or incorporated in the discontinuous phase, perforated microstructurεs or particles of thε present invention. Similarly, several techniques may be used to provide particulates having compatible physiochemical properties, morphology (i.e. a perforated configuration) and density. Among other methods, perforatεd microstructures or particles compatible with the instant invention may be formed by techniques including lyophilization, spray drying, multiple emulsion, micronization, or crystallization In prefεrrεd embodiments, relatively non-porous particles may be produced using techniques such as micronization, crystallization or milling. It will further be appreciated that, the basic concepts of many of these techniques are well known in thε pnor art and would not, in viεw of the teachings herein, require undue expεπmentation to adapt them so as to provide the desired particulates. While several procedures are generally compatible with the present invention, particularly preferred embodiments typically comprise particulates or perforatεd microstructurεs formεd by spray drying. As is wεll known, spray drying is a one-step process that converts a liquid feed to a dried particulate form. With respect to pharmaceutical applications, it will be appreciated that spray drying has been used to provide powdered material for various administrative routεs including inhalation. See, for examplε, M. Sacchεtti and M .M. Van Oort in: Inhalation Aerosols: Physical and Biological Basis for Therapy, A.J Hickey, ed. Marcel Dekkar, New York, 1996, which is incorporated herein by reference.

In general, spray drying consists of bringing togethεr a highly dispεrsed liquid, and a sufficient volume of hot air to produce evaporation and drying of the liquid droplets. The preparation to be spray dried or feed (or feed stock) can bε any solution, course suspension, slurry, colloidal dispersion, or paste that may be atomized using the selected spray drying apparatus. Typically, the feed is sprayed into a current of warm filtered air that evaporatεs the solvent and conveys thε dnεd product to a collector. The spεnt air is then εxhaustεd with the solvent. Those skilled in the art will appreciate that several different types of apparatus may be used to provide the desired product. For εxamplε, commercial spray dryers manufactured by Buchi Ltd or Niro Corp. will effεctively produce particles of desired size. It will furthεr bε appreciated that these spray dryers, and specifically their atomizers, may be modified or customized for specialized applications, i.e. thε simultanεous spraying of two solutions using a double nozzle technique. More specifically, a water-in-oil emulsion can be atomized from one nozzle and, a solution containing an anti adherεnt such as mannitol can be co atomized from a second nozzle. In other cases it may be desirable to push the feed solution though a custom designed nozzle using a high pressure liquid chromatography (HPLC) pump Provided that microstructures compπsing the correct morphology and/or composition are produced, the choice of apparatus is not cπtical and would be apparent to the skilled artisan in view of thε teachings herein.

While the resulting spray dried powdεrεd particles typically are approximately spherical in shape, nearly uniform in size and frequently are hollow, there may be some degree of irregularity in shape depending upon the incorporated medicament and the spray drying conditions. In many instances, the dispersion stability of spray dried microspheres or particles appεars to bε morε εffεctivε if an inflating agεnt (or blowing agent) is used in their production Particularly preferred embodimεπts may compnse an emulsion with the inflating agent as the disperse or continuous phase (the other phase being aqueous in nature) The inflating agent is preferably dispersed with a surfactant solution, using, for instance, a commercially available microfluidizer at a pressure of about 5,000 to 15,000 psi. This process forms an emulsion, preferably stabilized by an incorporated surfactant, typically compπsing submicron droplets of water immiscible blowing agent dispersεd in an aqueous continuous phase. The formation of such dispersions using this, and other tεchniquεs, are common and wεll known to those in the art Thε blowing agεnt is preferably a fluorinated compound (e g. perfluorohexane, perfluorooctyl bromide, perfluorodecalm, perfluorobutyl ethaπε) which vaporizes during the spray drying process, leaving bεhind generally hollow, porous aerodynamically light microspheres. As will be discussed in more detail below, other suitable blowing agents include chloroform, Freoπs, and hydrocarbons Nitrogen gas and carbon dioxide are also contemplated as suitable blowing agents

Although perforated microstructures are preferably formed using a blowing agent as described above, it will be appreciated that, in some instances, no additional blowing agent is required and an aquεous dispersion of the medicamεπt and surfactaπtls) are spray dried directly. In such cases, the formulation may be amenable to process conditions (ε g , εlevated tempεraturεs) that generally lead to thε formation of hollow, relatively porous microparticles. M oreover, the medicament may possess special physicochemical properties (e.g., high crystaliinity, elevatεd melting temperature, surface activity, etc.! that make it particularly suitable for use in such tεchniquεs.

When a blowing agent is εmployεd, the degreε of porosity of the perforated microstructure appears to depεnd, at least in part, on the nature of the blowing agent, its concentration in the feed stock (i.e as an emulsion), and the spray drying conditions. With respect to controlling porosity, it has surprisingly been found that the use of compounds, heretofore unappreciated as blowing agents, may provide particulates or perforatεd microstructurεs having particularly desirable characteristics More particularly, in this novel and unexpεctεd aspεct of thε presεnt invention, it has been found that the use of fluorinated compounds having relatively high boiling points (i.e. greater than about 60°C) may be usεd to produce particulates that are especially suitable for inhalation therapiεs. In this rεgard, it is possible to use fluorinated blowing agεnts having boiling points of greatεr than about 70°C, 80°C, 90°C or even 95°C. Particularly prefεrrεd blowing agεnts havε boiling points greater than the boiling point of water, i.e. greater than 100°C (e g. perflubron, perfluorodecalm) In addition, blowing agents with relatively low water solubility ( < 10 ° M) are preferred since they enable the production of stable emulsion dispersions with mean weighted particle diameters less than 0.3 urn. As indicated above, thεsε blowing agents will preferably be incorporated in an emulsified feed stock prior to spray drying For the purposes of the present invention this feed stock will also preferably comprise one or more bioactive agεnts, onε or more surfactants, or one or morε excipients. Of course, combinations of the aforemεntioned components are also within the scope of the invention.

While not limiting the invention in any way, it is hypothesizεd that, as thε aquεous feed component evaporates during spray drying it leaves a thin crust at the surfacε of thε particle. The resulting particle wall or crust, formed during thε initial momεnts of spray drying, appεars to trap any high boiling blowing agεnts as hundreds of emulsion droplets (ca. 200 300 nm). As the drying process continues, thε pressure inside the particulate increases, thereby vaporizing at least part of the incorporated blowing agent and, forcing it through the relatively thin crust. This venting or outgassing, apparently leads to the formation of pores or other defects in the crust. At thε same time, remaining particulate components (possibly including some blowing agεnt) migrate from the interior to the surface as the particle solidifies. This migration apparently slows during the drying process as a result of increasεd resistance to mass transfer caused by an increased internal viscosity. Once thε migration ceases, the particle solidifies, leaving vesicles, vacuoles or voids where the emulsifying agent resided. The number of pores, their sizε, and thε resulting wall thickness is largely depεndεnt on thε naturε of thε sεlεctεd blowing agεnt (i.e. boiling point), its concentration in the emulsion, total solids concentration, and the spray drying conditions.

It has been surprisingly found that substantial amounts of these relatively high boiling point blowing agents may be retained in the resulting spray dπεd product. That is, thε spray dried perforated microstructures may comprise as much as 5%, 10%, 20%, 30% or even 40% w/w of the blowing agent. In such cases, higher production yields were obtained as a result an increased particle density caused by residual blowing agεnt It will bε apprεciatεd by thosε skilled in the art that, this retained fluorinated blowing agent may alter the surface characteristics of the perforated microstructurεs and further increase the stability of the respiratory dispersions Conversely, the residual blowing agent can easily be rεmovεd with a post production εvaporation stεp in a vacuum ovεn. Optionally, porεs may be formed by spray drying a bioactive agεnt and an εxcipiεnt that can bε rεmovεd from thε formεd microspheres under a vacuum. In any εvent, typical concentrations of blowing agent in the fεεd stock are betweεn 5% and 100% w/v, and more prefεrably, bεtwεεn about 20% to 90% w/v. In othεr εmbodimεπts, blowing agent concentrations will prefεrably bε greater than about 10%, 20%, 30%, 40% 50% or even 60% w/v Yet other feed stock emulsions may comprise 70%, 80%, 90% or evεπ 95% w/v of thε sεlεctεd high boiling point compound.

In prεferred embodiments, another method of identifying thε concentration of blowing agent usεd in thε feed is, to provide it as a ratio of the concentration of thε blowing agent to that of the stabilizing surfactant (i.e. phospholipid) in the precursor emulsion For fluorocarbon blowing agents such as perfluorooctyl bromide and phosphatidylcholme, the ratio may bε termed a pεrfluorocarbon/phosphatidylcholinε ratio (or PFC/PC ratio). Of course, it will be appreciated that other compatible surfactants may also be used to provide compatible particulates In any event, thε PFC/PC ratio will typically range from about 1 to about 60 and more prefεrably, from about 10 to about 50 For preferred embodiments the ratio will geπεrally be greater than about 5, 10, 20, 25, 30, 40 or evεn 50 In this respect, Fig 1 shows a series of pictures taken of perforatεd microstructures formed of phosphatidylcholme (PC) using various amounts of perfluorooctyl bromide (PFC), a relatively high boiling point fluorocarbon as the blowing agent The PFC/PC ratios are provided under each subset of pictures, i e from

1 A to 1 F Formation and imaging conditions are discussed in greater detail m Examples I and II below. With regard to thε micrographs, thε column on the left shows the intact microstructurεs while the column on the right illustrates cross sections of fractured microstructures from thε samε preparations

As may easily be seεπ in thε Fig 1 , the use of higher PFC/PC ratios provides structures of a morε hollow and porous nature More particularly, those methods employing a PFC/PC ratio of greater than about 4 8 tended to provide structures that are particularly compatible with the dispersions disclosεd herein Similarly, Fig 2, a micrograph which will be discussed in more detail in Example II below, illustrates a preferably porous morphology obtained by using higher boiling point blowing agents (in this case perfluorodecalm)

While relatively high boiling point blowing agents comprise onε prεfεrrεd aspεct of thε instant invention, it will be appreciated that more conventional blowing or inflating agents may also bε usεd to provide compatible perforated microstructurεs. Generally, the inflating agent can be any mateπai that will turn to a gas at some point dunng the spray drying or post production process Suitable agents include 1 Dissolved low boiling (below 100 C) solvents with limited miscibility with aqueous solutions, such as methylene chlonde, acetonε and carbon disulfidε usεd to saturate the solution at room tεmperature 2 A gas, e g C0₂ or N-,, usεd to saturate the solution at room tempεraturε and εlevated pressurε (ε g. 3 bar). Thε droplets are thεn supεrsaturatεd with the gas at 1 atmosphere and 100 C 3 Emulsions of immiscible low boiling (below 100 C) liquids such as Freon 1 13 perfluoropeπtane pεrfluorohεxane, perfluorobutanε, pentane, butanε, FC 1 1, FC 11 B1, FC 1 1 B2, FC 12B2, FC 21 , FC 21 B1, FC

21 B2, FC 31 B1, FC 1 13A, FC 122, FC 123, FC 132, FC 133, FC 141 , FC 141 B, FC 142, FC 151, FC 152, FC 1112, FC 1 121 and FC 1131

With respect to these lower boiling point inflating agents, they are typically added to the feed stock in quantities of about 1 % to 40% v/v of the surfactant solution Approximately 15% v/v inflating agent has beεn found to producε a spray dπεd powder that may be used to form the stabilized dispersions of thε presεnt invention

Regardless of which blowing agent is ultimately selεctεd, it has bεen found that compatible pεrforated microstructures or particles may be produced particularly efficiently using a Buchi mini spray drier (model B 191 ,

Switzerland) As will be apprεciated by thosε skilled in the art the inlet tempεraturε and thε outlet temperature of the spray drier are not critical but will bε of such a level to provide the desired particle size and to result in a product that has thε dεsired activity of thε medicament In this regard, thε inlet and outlet temperatures are adjusted depεnding on thε melting characteristics of the formulation components and the composition of the feed stock. The inlet tempεraturε may thus be bεtwεεn 60°C and 170°C, with thε outlεt tεmpεratures of about 40°C to 120°C depending on the composition of the feed and the desired particulate characteristics. Preferably, these temperatures will be from 90°C to 120°C for the inlet and from 60°C to 90°C for the outlet The flow rate which is used in the spray drying εquipment will generally be about 3 ml pεr minutε to about 5 ml pεr minute. The atomizer air flow rate may vary between values of 1 ,200 liters per hour to about 3,900 liters per hour. Commercially available spray dryers are wεll known to those in the art, and suitable sεttings for any particular dispersion can be readily detεrmiπεd through standard empirical testing, with due reference to the examples that follow. Of course, the conditions may be adjusted so as to presεrvε biological activity in larger molecules such as proteins or peptides.

Particularly preferred embodimεnts of thε present invention compnse spray drying preparations comprising a surfactant such as a phospholipid and at lεast one bioactive agent. In other εmbodimεπts, thε spray drying preparation may further comprise an excipiεnt compnsing a hydrophilic moiety such as, for examplε, a carbohydrate |ι e glucose, lactose, or starch) in addition to any selectεd surfactant. In this rεgard, various starchεs and dεπvatized starches are suitablε for usε in the presεnt invention. Other optional components may include conventional viscosity modifiers, buffers such as phosphate buffers or, other conventional biocompatible buffers or pH adjusting agents such as acids or bases, and osmotic agents (to providε isotonicity, hyperosmolaπty, or hyposmolanty). Examples of suitable salts include sodium phosphate (both monobasic and dibasic), sodium chloride, calcium phosphate, calcium chloride and other physiologically acceptable salts. Whatever components are selected, the first step in particulate production typically comprises feed stock preparation Preferably, the selectεd drug is dissolved in water to produce a concentrated solution The drug may also be dispersed directly in the emulsion, particularly in the case of water insoluble agents Alternatively, thε drug may bε incorporated in the form of a solid particulate dispersion. The concentration of thε drug used is dependent on the dose of drug required in the final powder and the performance or efficiency of the nebulization devicε As nεeded, co surf actants such as poloxamεr 188 or span 80 may bε addεd to this anπεx solution. Additionally, excipients such as sugars and starches can also be added

In selectεd εmbodimεnts, an oil in watεr εmulsion is then formed in a separate vessel. The oil εmployed is preferably a fluorocarbon (e.g., perfluorooctyl bromide, perfluorodecalm), which is emulsified using a surfactant such as a long chain saturated phospholipid For examplε, onε gram of phospholipid may be homogenized in 1 50 g hot distilled water (e.g., 60°C) using a suitable high shear mechanical mixer (e.g.. Ultra Turrax model T 25 mixer) at 8000 rpm for 2 to 5 minutes Typically, 5 to 25 g of fluorocarbon is added dropwise to the dispersεd surfactant solution whilε mixing. The resulting perfluorocarbon iπ-water εmulsion is thεπ processed using a high pressurε homogεnizer to reduce the particle size. Typically, the emulsion is processεd at 12,000 to 18,000 psi, 5 discrete passes and kept at 50 to 80°C.

Thε drug solution and perfluorocarbon emulsion are then combined and fed into the spray dryεr Typically, thε two preparations will be miscible as thε emulsion will preferably comprise an aqueous continuous phase. While the bioactive agent is solubilized separately for the purposes of the instant discussion, it will be appreciated that, in other embodiments, the bioactive agεnt may bε solubilized (or dispersed) directly in the emulsion In such cases, thε bioactivε εmulsion is simply spray dπεd without combining a sεparatε drug preparation.

In any event, operating conditions such as inlet and outlεt tεmpεrature, feεd ratε, atomization pressurε, flow ratε of thε drying air, and nozzle configuration can be adjusted in accordance with the manufacturer's guidelines in order to produce the required particle size and production yield of the resulting dry microstructures Exemplary settings are as follows: an air inlet temperature between 60°C and 170°C; an air outlet bεtwεen 40°C to 120°C, a feed rate between 3 ml to about 15 ml per minute, and an aspiration setting of 300 L/min and an atomization air flow rate betwεeπ 1 ,200 to 2,800 L/hr The selection of appropriate apparatus and processing conditions are well within the purviεw of a skilled artisan in view of the tεachings herein, and may be accomplished without undue expεπmentation. In any event, the use of these and substantially equivalent methods provide for thε formation of hollow, porous, aerodynamically light microspheres, with particle diameters appropriate for aerosol deposition into the lung. As described above, such particles are particularly effεctive in the formation of stabilized dispersions that are extrεmεly compatiblε with thε inhalation systεms and nebulization techniques described more fully below.

Along with spray drying, particulates or perforated microstructures useful in the presεnt invention may be formεd by lyophilization Thosε skilled in the art will appreciate that lyophilization is a freεzε drying process in which water is sublimed from thε composition after it is frozen The particular advantage associated with the lyophilization process is that, biologicals and pharmaceuticals that are relatively unstable in an aqueous solution can be dried without elevated temperatures (thereby eliminating the adverse thermal effεcts), and thεn stored in a dry state where there are few stability problems. With respεct to thε instant invention, such techniques are particularly compatible with thε incorporation of pεptidεs, protεins, gεnetic material and other natural and synthetic macromoleculεs in particulates or perforated microstructures without compromising physiological activity Methods for providing lyophihzed particulates are known to thosε of skill in thε art and, it would clearly not require undue experimentation to provide dispersion compatible microstructurεs in accordance with the teachings herein Accordingly, to the extεnt that lyophilization processes may bε used to providε microstructurεs having the desired porosity and size, they are in conformance with the teachings herein and are expressly contemplated as being within the scope of the instant invention.

In addition to the aforementioned techniques, pεrforated microstructurεs or particles of the presεnt invention may also be formed using a double emulsion method. In the double emulsion method, the medicamεπt is first dispersed in a polymer dissolved in an organic solvent (e.g mεthylεnε chloride) by sonication or homogenization. This primary emulsion is then stabilized by forming a multiple emulsion in a continuous aqueous phase containing an emulsifier such as polyvinylalcohol Thε organic solvent is then removed by evaporation or extraction using conventional techniques and apparatus. The resulting microspheres are washed, filtered and lyophihzed prior to dispersion into suspension medium in accordance with the present invention While particulate suspensions comprising a non liquid dispersed phase are particularly compatible with the present invention, it will be appreciatεd that, as discussed above, the stabilized dispersions may also comprise Iiquid-in-iiquid colloidal systems, e.g. reverse emulsions and microεmulsioπs. Those skilled in the art will appreciate that such systems are known in the art and stabilized dispersions compatible with the teachings herein may be provided without undue experimentation. In this regard, any reverse emulsion or microemulsioπ that is capable of being nebulized to providε a thεrapεutically effective aerosol for pulmonary administration is contemplatεd as being within the scope of the present invention. Preferably, the emulsions will be water-in-fluorochemical emulsions. That is, thε sεlected reverse emulsion or microemulsion will prefεrably comprise a fluorochemical disperse phase with the other phase being aquεous in nature. Exemplary reverse emulsions useful with the present invention are disclosεd in U S. Pat No 5,770,585, pεnding U S S N. 08/487,612 and pεnding U S.S.N. 08/478,824 with εach of the foregoing references incorporated herein by reference. Such preparations may be stabilized by fluorinated or non fluorinated surfactants. With rεspεct to this aspεct of the invention, many of the fluorochemicals useful in the disclosed liquid in liquid preparations are the same as those that are useful as suspension mediums in the disclosεd particulate dispersions Accordingly, while thε following discussion is primarily directed to compatible suspension mediums for the distribution of non liquid particles, it will be apprεciated that the same compounds (e.g fluorochemicals) are useful in liquid in liquid dispersions that are compatible with the instant invention. Thus, while the term "suspension medium" or media will bε usεd bεlow, it should bε undεrstood that, these same compounds may comprise emulsion phases in accordancε with thε tεachiπgs herein.

Regardlεss of the selεcted colloidal system, it is an advantage of the presεnt mvεπtion that biocompatible nonaqueous compounds may be used as suspension mεdiums or as a continuous phase. Particularly prefεrred suspension media are compatible with usε in nebulizers. That is, they will bε able to form aerosols upon the application of energy thereto. In general, the selected suspension medium should be biocompatible li e. relatively non toxic) and non reactive with respεct to thε suspεnded pεrforatεd microstructures compπsing thε bioactive agent Prefεrred embodiments compnse suspεnsion mεdia sεlεcted from the group consisting of fluorochemicals, fluorocarbons (including those substituted with other halogens), perfiuorocarbons, fluorocarboπ/hydrocarboπ diblocks, hydrocarbons, alcohols, ethers, or combinations thereof It will be appreciated that, the suspension medium may comprise a mixture of vaπous compounds selected to impart specific characteπstics. It will also be appreciated that the perforated microstructures are prefεrably insoluble in the suspension medium, thereby providing for stabilized medicament particles, and effectively protecting a selected bioactive agent from degradation, as might occur dunng prolonged storage in an aqueous solution. In prεfεrrεd εmbodiments, the selεctεd suspεnsion mεdium is bactεπostatic. Thε suspεnsion formulation also protects the bioactive agent from degradation dunng the nebulization process.

As indicated above the suspεnsion media may comprise any one of a number of different compounds including hydrocarbons, fluorocarbons or hydrocarbon/fluorocarboπ diblocks. In general, the contemplated hydrocarbons or highly fluorinated or perfluoπnatεd compounds may be linear, branched or cyclic, saturated or unsaturatεd compounds. Conventional structural derivatives of these fluorochemicals and hydrocarbons are also contemplatεd as bεiπg within the scope of the present invention as well. Selεctεd εmbodimεnts compπsing thεsε totally or partially fluorinated compounds may contain one or more hetero-atoms and/or atoms of bromine or chloπne. Prefεrably, thεsε fluorochemicals compose from 1 to 16 carbon atoms and include, but are not limited to, linear, cyclic or polycyclic pεrfiuoroalkanεs, bιs(perfiuoroalkyl)alkεnes, perfluoroethers, perfluoroamiπεs, pεrfluoroalkyl bromides and perfluoroalkyl chloπdεs such as dichlorooctane Particularly prefεrrεd fluorinated compounds for use in the suspension medium may comprise perfluorooctyl bromide C₉F,₇Br (PFOB or pεrflubron), dichlorofluorooctane C₉F_1SCI₂ and thε hydrofluoroalkane perfluorooctyl ethanε C₈F₁₇C₂H₅ (PFOE). With respεct to othεr εmbodimεnts, thε usε of perfluorohexanε or perfiuoropeπtaπe as the suspension medium is especially preferred.

More generally, exemplary fluorochemicals which are contemplatεd for usε in the present invention generally include halogeπatεd fluorochemicals (i.e. C,F _n.|X, XCF₂„X, where n = 2 10, X = Br, Cl or I) and, in particular, 1 bromo F butanε n C„F₉Br, 1 bromo F hεxanε (n C₆F,₃Br), 1 bromo F hεptanε (n C₇F,₅Br), 1 ,4 dibromo F butanε and 1 ,6 dibromo F hexane. Other useful brαminated fluorochemicals are disclosed in US Patent No. 3,975,512 to Long and are incorporated herein by refεrεncε. Specific fluorochemicals having chlondε substituεnts, such as perfluorooctyl chloride (n C_ΘF,₇CI|, 1,8 dichloro F octane (n CIC₈F,₆CI), 1 ,6 dichloro-F-hexaπe (π CIC₆F,₂CI), and 1 , 4-dιchloro F butaπε (n-CIC₄F₈CI) are also preferred.

Fluorocarbons, fluorocarbon hydrocarbon compounds and halogenated fluorochemicals containing other linkage groups, such as esters, thioethεrs and aminεs are also suitable for use as suspension media in the present invention. For instance, compounds having thε general formula, C„F_2n.,OC_mF_2m4|, °' COiCH - CHC^F,^,, (as for example

C₄F₉CH= CHC₄F₉ (F 44E), i C₃F₉CH = CHC₆F_n (F ι36E), and C_SF,₃CH= CHC₆F₁₃ (F 66E)) where n and m are the same or different and n and m are integers from about 2 to about 12 are compatible with teachings herein. Useful fluorochemical- hydrocarbon diblock and tπblock compounds include those with the genεral formulas C,F₂„₄, C_mH₂^,, and C_nF_2n., C_mH_{2m l}, whεrε n = 2 12; m - 2 16 or C_PH_2p4, C„F₂„ CJl^.,, where p = 1 12, m = 1 12 and n - 2 12. Prefεrrεd compounds of this typε include C₀F, ,C₂H₆ C_SF,₃C₁₀H₂₁ C₈F, _?C₈H,₇ C_SF,₃CH=CHC₆H,₃ and C„F,₇CH=CHC_t0H₂₁. Substituted ethers or polyεthers (i ε XC,F_2η0C_mF_2πX, XCF0C_πF_2n0CF₂X, where n and m = 1 4, X = Br, Cl or I) and fluorochemical hydrocarbon ether diblocks or tπblocks (i.e. C„F_2l., 0 C B,_m.₍, where n = 2 10; m = 2 16 or C,H_2p 0 C,F-,_n 0 C_mH_2n1,ι, where p = 2 12, m = 1 12 and n = 2 12) may also used as well as C„F_2n,, 0 C_τF₂„.0C_pH_2p. ,, whεrein n, m and p are from 1 12

Furthεrmorε, depending on the application, perfluoroalkylated ethers or polyethεrs may bε compatible with the claimed dispersions.

Poiycyclic and cyclic fluorochemicals, such as C,₀F,₈ (F decaliπ or perfluorodecalm), perfiuoropεrhydrophεnanthrεnε, perfluorotetramethylcyclohexane (AP 144) and perfluoro n butyldecahn are also within thε scope of the invention. Additional useful fluorochemicals include perfluonnated amines, such as F tπpropylamine

("FTPA") and F tπbutylamme ("FTBA"). F 4 methyloctahydroquinolizinε ("FMOD"), F N methyl decahydroisoquinolinε ("FMIQ"), F N-mεthyldecahydroquiπoliπe ("FHQ"), F N cyclohexylpyrrolidine ("FCHP") and F 2 butyltεtrahydrofuraπ ("FC 75"or "FC 77") Still othεr usεful ftuoπnated compounds include perfluorophenanthrene, perfluoromethyldecalin, pεrfluorodimethylethylcyclohexanε, perfluorodimethyldecaliπ, perfluorodiethyldecalin, perfluoromethyladamantane, perfluorodimethyladamantane Othεr contεmplatεd fluorochεmicals having nonfluoπnε substituεnts, such as, perfluorooctyl hydnde, and similar compounds having different numbers of carbon atoms are also usεful. Those skilled in the art will further appreciatε that othεr variously modified fluorochemicals are εncompassed within the broad definition of fluorochemical as used in the instant application and suitable for use in the present invention. As such, each of the foregoing compounds may be used, alone or in combination with other compounds to form thε stabilized dispersions of thε present invention.

Specific fluorocarbons, or classes of fiuonnated compounds, that may bε useful as suspεnsion media include, but are not limited to fluoroheptaπε, fluorocyclohεptanε fluoromethylcyclohεptane, fiuorohεxaπe, fluorocyclohεxanε. fluoropεntanε, fluorocyclopεntaπε, fluoromεthylcyclopentane fluorodimethylcyclopεntanes, fluoromethylcyclobutanε, fluorodimethylcyclobutaπe, fluorotnmethylcyclobutane, fluorobutanε, fluorocyclobutane, fluoropropaπe, fluoroethers, fluoropolyethεrs and fluorotπεthylaminεs. Such compounds are generally environmεntally sound and are biologically non reactive.

While any fluid compound capable of producing an aerosol upon the application of εnεrgy may bε usεd in conjunction with thε prεsεπt invention, the selεcted suspεnsion mεdium will preferably have a vapor pressure less than about 5 atmospheres and more prefεrably lεss than about 2 atmosphεrεs Unless othεrwisε specified, all vapor pressures recited herein are measured at 25°C. In other embodimεnts, prεferred suspension media compounds will have vapor pressures on the order of about 5 torr to about 760 torr, with more preferable compounds having vapor pressures on the order of from about 8 torr to about 600 torr, while still more preferable compounds will have vapor pressures on the order of from about 10 torr to about 350 torr. Such suspension media may bε usεd in conjunction with compressed air nebulizers, ultrasonic nebulizers or with mechanical atomizers to provide effective ventilation therapy. Moreovεr, morε volatile compounds may be mixed with lower vapor pressurε components to provide suspension media having specified physical charactenstics sεlεcted to further improve stability or enhance the bioavailabi ty of thε dispersεd bioactivε agent. Other embodimεnts of thε prεsεnt invention will compnse suspension media that boil at sεlεcted tempεraturεs uπdεr ambiεnt conditions (i.e. 1 atm). For εxamplε, prεfεrrεd embodiments will compose suspension media compounds that boil above 0°C, above 5°C, above 10°C, above 15°, or above 20°C In other embodimεnts, thε suspension media compound may boil at or above 25°C or at or above 30°C. In yet other embodiments, the selected suspension media compound may boil at or above human body tempεraturε (i ε 37°C), abovε 45°C, 55°C, 65°C, 75°C, 85°C or above 100°C.

It will further be apprεciated that onε of ordinary skill in thε art can readily detεrminε othεr compounds that would perform suitably in the presεnt invention which apparently do not exhibit a desirable vapor pressure and/or viscosity Rather, it will be understood that, certain compounds outsidε the preferred ranges of vapor pressure or viscosity can be used if they provide the desired aerosolized medicament. The stabilized suspensions or dispersions of the prεsεnt invention may be prepared by dispεrsal of thε microstructurεs in thε sεlected suspension mεdium which may then bε placεd in a container or reservoir. In this regard, thε stabilized preparations of thε presεnt invention can be made by simply combining the components in sufficient quantity to produce the final dεsired dispersion concentration Although the microstructures readily disperse without mechanical energy, the application of mechanical enεrgy to aid in dispersion (e.g with the aid of sonication) is contemplated, particularly for the formation of stable εmulsions or rεvεrse emulsions Alternatively, the components may be mixed by simple shaking or othεr type of agitation Thε process is preferably carried out uπdεr anhydrous conditions to obviate any adverse effεcts of moisture on suspension stability Once formεd, the dispersion has a reduced susceptibility to flocculation and sεdimεntation

It will also be understood that, other components can be included in the pharmaceutical compositions of the present invention For εxamplε, osmotic agεnts, stabilizers, chelators, buffers, viscosity modulators, salts, and sugars can be added to fine tune the stabilized dispersions for maximum life and ease of administration. Such components may be added directly to the suspension medium, ethεr phase of an emulsion or associated with or incorporated in, dispersεd particles or perforatεd microstructures. Considerations such as stenlity, isotonicity, and biocompatibility may govern the use of conventional additives to thε disclosεd compositions Thε usε of such agεnts will bε undεrstood to thosε of ordinary skill m the art and, thε specific quantities, ratios, and types of agents can be determined empirically without undue expεnmεntation

Administration of bioactive agent may be indicated for the treatmεπt of mild, modεratε or severe, acute or chronic symptoms or for prophylactic treatment Moreover, the bioactive agent may be administered to treat local or systemic conditions or disorders. It will bε appreciated that, the precise dose administered will dεpεnd on thε age and condition of the patient, the particular medicamεπt used and the frequency of administration, and will ultimately be at the discretion of thε attεndant physician Whεn combinations of bioactivε agεnts are εmployεd, thε dose of εach component of the combination will generally be that empioyεd for εach component when usεd alone. As discussed throughout the specification, thε stabilized dispersions disclosed herein, are prefεrably administεred to thε lung or pulmonary air passages of a patient via aerosohzation, such as with a nebulizer. Nebulizers are well known in the art and could easily be εmployεd for administration of thε claimed dispεrsions without unduε εxpeπmeπtation. Breath activated nebulizers, as well as those compπsing other types of improvements which have been, or will be, developed are also compatible with the stabilized dispersions and presεnt invention and are contemplated as being with in the scope thereof.

While compatible bioactivε agεnts may bε administεred using various systεms, it will be appreciated that, in particulariy prεfεrrεd embodiments, the stabilized dispersions disclosed herein will be administered to the lung or pulmonary air passages of a patient via nebulization Nebulizers are well known in thε art and could easily be employed for administration of the claimed dispersions without undue experimentation. Nebulizers work by forming aerosols, that is converting a bulk liquid into small droplets suspεndεd in a breathable gas. Here, the aerosolized medicament to be administered (prefεrably to thε pulmonary air passages) will compnse small droplets of suspension medium associated with relatively non porous particles, perforated microstructures, or disperse liquid phase compnsing a bioactive agent. In such embodiments, the stabilized dispersions of the present invention will typically be placεd in a fluid resεrvoir opεrably associated with a nebulizer. The specific volumes of preparation provided, means of filling thε reservoir, etc., will largely bε dεpendeπt on the selection of the individual nebulizer and is well within the purview of thε skilled artisan. Of course, the present invention is entirely compatible with single dose nebulizers and multiple dosε nebulizers.

In any event, nebulizer mεdiatεd aerosohzation typically requires an input of εnεrgy in ordεr to producε thε increased surface area of the droplets and, in some cases, to provide transportation of the atomized or aerosolized medicament. Onε common modε of aεrosolization is forcing a stream of fluid to be ejected from a nozzle, whereby droplets are formed. With respect to nebulized administration, additional energy is usually imparted to provide droplets that will be sufficiently small to be transportεd dεep into the lungs Thus, additional enεrgy is nεεdεd, such as that provided by a high velocity gas stream or a piezoelectπc crystal. Two popular types of nebulizers, jet nebulizers and ultrasonic nebulizers, rely on the aforementioned methods of applying additional εnεrgy to thε fluid during atomization The jet nebulizer is well known and in widespread use. In a jet nebulizer, compressed air is forced into a devicε containing a liquid to bε aerosolized, such as one of the suspεnsions of thε prεsεnt invention. The compressed air draws the liquid through one or more small openings, thus generating the aerosol. The high velocity of the compressεd air provides sufficient enεrgy to εnablε the foπnation of droplets small εnough for inhalation To aid in formation of uniformly smaller droplets, the droplεts initially impact a bafflε. Thεre may be othεr impaction sites onto which the droplets may be directed before the aerosol is earned out of the nebulizer by the flow of the compressed air. In preferred embodiments the compressed air may be saturated with the suspension medium. This would allow the aerosolized droplets to be deposited in the lung, possibly facilitating enhanced spreading of bioactive agεnt aftεr initial deposition. Ultrasonic nebulizers do not require the use of comprεssεd air, and thus, may be similar to MDIs as to compactness and portability, though they operatε under different physical pnnciples. Preferred ultrasonic nebulizers are those which are fairly small, portable, battery powεrεd and capable of dehvεπng sεvεral dosεs, εach of which comprises a single bolus of aerosolized solution. Such nebulizers may be termed single-bolus nebulizers. Most devices are manually actuated, but some devices exist which are breath actuated. Breath actuatεd devices work by releasing aerosol when the device senses the patiεnt inhaling through a circuit. Breath actuated nebulizers may also be placεd in line on a ventilator circuit to release aerosol into the air flow which compnses the inspiration gases for a patient.

The heart of most species of ultrasonic nebulizer is a transducer made from a piezoεlεctπc crystal. When oscillating enεrgy is applied to the piezoelectric crystal, it will vibrate at the same frequεncy as thε applied εnergy which is preferably in the ultrasonic range. This motion, when transmitted into a liquid, provides the energy nεεded to aerosolize the liquid. The droplet size (count median diameter) formed by this method is a function of the excitation frequency, the density of the liquid, and thε surfacε tεπsion of the liquid, whereas thε ratε of atomization is a function of thε viscosity, surfacε tension, and vapor pressure.

One type of nebulizer is the Respimat (Boεhπngεr Ingεlheim, Germany) which is manually actuated, hand-held and battery operated When the patient squεεzes a tngger on thε device, a droplet of solution (about 100 I) is metεred into a piezoelectric plate about 1 cm in diameter. Whεπ εnergy is applied, the plate vibratεs at about 10 MHz, resulting in the aerosohzation of thε solution which may then be inhaled by a patient.

Another type of ultrasonic nebulizer is the AeroDose (AεroGεn, Sunnyvale, CA). (DeYoung, "The AeroDose Multidosε Inhaler Devicε Dεsign and Delivery Charactenstics," Respiratory Drug Delivery VI, 1998, p. 91 ) The battery powered AeroDose operates by means of a platε containing several hundred holes which vibrates at ultrasonic frequencies. When thε top of the devicε is pressed down, a metenng pump delivers a dose of liquid from a multidose canister to the plate. The device is breath actuated, with aerosohzation beginning when the devicε sεπsεs thε inspiration of thε patiεnt. Thε investigators for the AeroDosε report that they are able to achieve a median mass aerodynamic diameter of 1.9 to 2.0 m using this device.

Yet another type of ultrasonic nebulizer is that in PCT Publication No. W092/1 1050 to Robertson, et. al., In the Robertson device, the solution or other mateπai to be nebulized is drawn through numerous tiny holes in a metal plate which vibratεs through thε usε of a piezoelectric device When enεrgy is applied, thε aerosol is formed and will continue to form as long as eπεrgy is delivered to the piezoelectπc crystal. Thus, depεπding on thε amount of time that the device is left on, it may serve as εithεr a single bolus devicε or a continuous nebulizer. As sεεn abovε, ultrasonic nebulization devices may act by ultrasonic enεrgy alonε, or may usε ultrasonic εnεrgy in combination with other methods of aerosohzation such as forcing or drawing a liquid or suspension through a matenal with very small openings. Yet, regardless of the type of nebulizer selectεd, thε stabilized dispersions of thε prεsεnt invention provide a significant advantage due to their relatively homogeneous dispersion of thε incorporated bioactive agent over a pεπod of time. That is, the homogenεous dispersion of the incorporated particulates ensures that the amount of bioactive agεnt administεred will be consistent no matter which fraction of the preparation in the fluid resεrvoir is actually nebulized in each individual actuation of the nebulizer. Similarly, when used for continuous administration over an extended period the stable, homogenεous dispersions of thε present invention ensure that relatively constant levels of bioactive agεnt are delivered during each incremental period of time. In any event, it should be noted that the preceding examples of πebuhzεrs are only for εxεmplary purposes. As will be recognized by one skilled in the art, othεr types of nebulizers, whethεr currently known or later invented, may also be used for administration of the stabilized dispersions of the present invention.

It will be appreciated that, thε stabilized preparations for use in nebuiizεrs of thε prεsεnt invention may bε advantageously supplied to the physician or other health care professional, in a sterile, prepackaged or kit form. More particularly, the formulations may be supplied as stable, preformεd dispεrsions rεady for administration or, as sεparatε rεady to mix components. When provided in a ready to use form, the dispersions may be packaged in single usε containεrs or rεsεrvoirs, as wεll as in multi usε containεrs or rεservoirs. in either case, the container or reservoir may be associated with the sεlεcted nebulizer and used as dεscπbεd hεreiπ. When provided as individual components (e.g., as powdered microspheres and as neat suspension medium) thε stabilized preparations may then be formed at any time prior to use by simply combining the contents of thε containεrs as directed. Additionally, such kits may contain a number of ready to mix, or prepackaged components that may be packaged individually so that thε usεr can then select the desired componeπt(s) for thε particular indication or usε. In this rεgard, the usεr may than substitutε sεlεcted components at will, or as indicated, during a particular course of treatment. It will also be appreciated that such kits may optionally include a nebulizer or that the preparation may be supplied in a disposable nebulizer.

The foregoing description will bε morε fully undεrstood with reference to the following Examples. Such Examples, are, howevεr, mεrεly rεpresεntativε of prεferred methods of practicing thε prεsεnt invention and should not be read as limiting the scope of the invention.

Preparation of Hollow Porous Particles of Gentamicin Sulfate by Spray Drying 40 to 60ml of the following solutions were preparεd for spray drying. 50% w/w hydrogenated phosphatidylcholme, E 100 3 (Lipoid KG, Ludwigshafen, Gεrmany) 50% w/w gentamicin sulfate (Amresco, Solon, OH) Pεrfluorooctylbromidε, Pεrflubron (NMK, Japan) Deionized water

Perforated microstructures comprising gεπtamiciπ sulfate were prepared by a spray drying technique using a B 191 Mini Spray Drier (Buchi, Flawil, Switzerland) under the following conditions: aspiration: 100%, inlet temperature: 85°C; outlet tempεraturε: 61 °C; feed pump: 10%; N₂ flow. 2,800 L/hr. Variations in powder porosity were εxamined as a function of thε blowing agεnt concentration. Fluorocarboπ-in-water εmuisions of pεrfluorooctyl bromidε containing a 1.1 w/w ratio of phosphatidylcholme (PC), and gentamicin sulfate were preparεd varying only thε PFC/PC ratio. 1 3 grams of hydrogenated egg phosphatidylcholme was dispersεd in 25 mL deionized water using an Ultra-Turrax mixer (model T 25) at 8000 rpm for 2 to 5 minutes (T = 60 70°C). A range from 0 to 40 grams of perflubron was added dropwise dunng mixing (T = 60 70°C). After addition was complete, the fluorocarbon m-water emulsion was mixed for an additional period of not less than 4 minutes. The resulting coarse εmuisions were then homogεmzed under high pressure with an Avestin (Ottawa, Canada) homogemzer at 15,000 psi for 5 passes. Gentamicin sulfate was dissolved in approximately 4 to 5 mL deionized water and subsεquεntly mixεd with thε perflubron emulsion immediatεly prior to thε spray dry process. The gentamicin powders were then obtained by spray drying using the conditions described abovε. A free flowing palε yεllow powdεr was obtainεd for all pεrflubron containing formulations. The yield for each of the various formulations ranged from 35% to 60%.

Morphology of Gentamicin Sulfate Spray Dπεd Powdεrs A strong dependence of the powdεr morphology, dεgrεe of porosity, and production yield was observεd as a function of thε PFC/PC ratio by scanning εlεctron microscopy (SEM). A series of six SEM micrographs illustrating these observations, labeled 1 A1 to 1 F 1 , are shown in the left hand column of Fig. 1. As seen in these micrographs, the porosity and surfacε roughnεss was found to bε highly dεpεndεnt on the concentration of the blowing agent, whεrε the surfacε roughnεss, πumbεr and size of the pores increased with increasing PFC/PC ratios. For examplε, the formulation devoid of perfluorooctyl bromidε produced microstructures that appeared to be highly agglomeratεd and readily adhered to the surface of the glass vial. Similarly, smooth, spherically shaped microparticles wεrε obtainεd whεn relatively little (PFC/PC ratio = 1 1 or 2.2) blowing agent was usεd As thε PFC/PC ratio was increased the porosity and surfacε roughπεss increased dramatically.

As shown in the right hand column of Fig. 1 , the hollow nature of the microstructurεs was also επhancεd by thε incorporation of additional blowing agεnt. Morε particularly, thε series of six micrographs labeled 1 A2 to 1 F2 show cross sεctions of fractured microstructurεs as rεvεalεd by transmission εlεctron microscopy (TEM). Each of thεsε imagεs was producεd using thε same microstructure preparation as was used to produce the corresponding SEM micrograph in the left hand column. Both the hollow nature and wall thickness of the resulting perforated microstructures appeared to be largely dependent on the concentration of the selected blowing agent. That is, the hollow naturε of thε preparation appεared to increase and the thickness of the particle wails appeared to decrεasε as the PFC/PC ratio increased. As may be seεπ in Figs. 1 A2 to 1 C2 substantially solid structures werε obtainεd from formulations containing little or no fluorocarbon blowing agent Conversely, the perforated microstructures producεd using a relatively high PFC /PC ratio of approximately 45 (shown in Fig. 1 F2 proved to be εxtrεmεly hollow with a relatively thin wall ranging from about 43.5 to 261 nm Both types of particles are compatible for usε in the present invention.

Preparation of Hollow Porous Particles of Albuterol Sulfate by Spray Drying Hollow porous albuterol sulfate particles wεre prepared by a spray drying technique with a B 191 Mini Spray Drier (Buchi, Flawil, Switzεrland) undεr the following spray conditions- aspiration: 100%, inlet temperature-

85° C; outlet temperature: 61 °C; feed pump: 10%; N, flow: 2,800 L/hr. The feed solution was prepared by mixing two solutions A and B immediately prior to spray drying.

Solution A. 20g of water was used to dissolve 1 g of albuterol sulfate (Accurate Chemical, Westbury, NY) and 0 021 g of poloxamer 188 NF grade (BASF, Mount Olive, NJ) Solution B. A fluorocarbon in water emulsion stabilized by phospholipid was preparεd in thε following mannεr Thε phospholipid, 1 g EPC 100 3 (Lipoid KG, Ludwigshafen, Germany), was homogenized in 150g of hot deionized water (T = 50 to 60°C) using an Ultra Turrax mixεr (model T 25) at 8000 rpm for 2 to 5 minutes (T = 60 70°C). 25g of perfluorooctyl bromide (Atochem, Pans, France) was added dropwisε during mixing After thε fluorocarbon was addεd, thε emulsion was mixed for a period of not less than 4 minutes. The resulting coarse emulsion was then passed through a high pressure homogemzεr (Avεstin, Ottawa, Canada) at 18,000 psi for 5 passεs.

Solutions A and B wεre combiπεd and fed into the spray-dryer under the conditions described above. A freε flowing whitε powdεr was collected at the cyclone separator The hollow porous albuterol sulfate particles had a volume-weighted mean aerodynamic diameter of 1.18 ± 1 42 μm as determiπεd by a time-of flight analytical method (Aerosizer, Amherst Process Instruments, Amherst, MA) Scanning εlεctron microscopy (SEM) analysis showεd thε powdεrs to bε spheπcal and highly porous. The tap density of the powdεr was dεtεrminεd to be less than 0 1 g/cm³ This foregoing example servεs to illustrate the inherent diversity of the prεsεnt invεntion as a drug dεhvεry platform capable of effectively incorporating any one of a number of pharmaceutical agents. The pππcφiε is furthεr illustrated in the nεxt εxamplε.

IV Formation of Porous Particulate Microstructures Compnsing Mixtures of Long-Chain/Short Chain Phospholipids and Albutεrol Sulfate A dispersion for spray-drying was preparεd as described above, with the difference that 1 g of DSPC was dispersed with 100 mg of a short chain phospholipid, dioctylphosphatidylcholine (DOPC) (Avanti Polar Lipids, Alabastεr, Alabama). The composition of the spray fεed is shown in Table II immediately below. The resulting yield was 50%.

Table II

Composition of the Spray Feed

V

Preparation of Hollow Porous Particles of Cromolyn Sodium by Spray Drying Perforated microstructures comprising cromolyn sodium were prepared by a spray-drying technique with a B 191 Mini Spray Drier (Buchi, Flawil, Switzerland) under the following spray conditions- aspiration- 100%, inlet temperature: 85° C, outlet tεmpεraturε: 61 °C, fεed pump. 10%; N, flow. 2,800 L/hr. Thε fεed solution was prepared by mixing two solutions A and B immediately prior to spray drying.

Solution A. 20g of water was used to dissolve 1 g of cromolyn sodium (Sigma Chemical Co, St. Louis, MO) and 0 021 g of poloxamer 188 NF grade (BASF, Mount Olive, NJ)

Solution B. A fluorocarbon in water emulsion stabilized by phospholipid was prepared in the following manner The phospholipid, 1 g EPC 100 3 (Lipoid KG, Ludwigshafen, Gεrmany), was homogεnizεd in 150g of hot deionized water (T - 50 to 60°C) using an Ultra-Turrax mixεr ( odεi T 25) at 8000 rpm for 2 to 5 minutes (T =

60 70°C). 27g of perfluorodecalm (Air Products, Allentown, PA) was addεd dropwisε during mixing. After the fluorocarbon was added, the emulsion was mixed for at least 4 minutes. The resulting coarse emulsion was then passed through a high pressure homogemzεr (Avεstin, Ottawa, Canada) at 18,000 psi for 5 passεs Solutions A and B wore combined and fed into the spray dryer under thε conditions described above. A free flowing pale yellow powder was collected at the cyclone sεparator. The hollow porous cromolyn sodium particles had a volume weighted mean aerodynamic diamεtεr of 1 23 ± 1 31 μm as dεtermmed by a timε of flight analytical mεthod (Aerαsizεr, Amhεrst Process Instruments, Amherst, MA). As shown in Fig. 2, scanning electron microscopy (SEM) analysis showed the powders to be both hollow and porous The tap density of the powdεr was determiπεd to bε less than 0.1 g/cm³.

VI Preparation of Hollow Porous Particles of BDP by Spray Drying Perforated microstructures comprising beclomεthasonε dipropionate (BDP) particles were prepared by a spray drying techniquε with a B 191 Mini Spray Dπεr (Buchi, Flawil, Switzεrland) undεr thε following spray conditions: aspiration: 100%, inlet temperature: 85°C, outlet tempεraturε: 61 °C; fεεd pump: 10%; N₂ flow: 2,800 L/hr Thε feed stock was prepared by mixing 0.1 1 g of lactose with a fluorocarbon in water emulsion immεdiatεly prior to spray drying. The emulsion was prepared by the technique described below. 74 mg of BDP (Sigma, Chemical Co , St Louis, MO), 0 5g of EPC 100 3 (Lipoid KG, Ludwigshafen,

Germany), 15mg sodium oleatε (Sigma), and 7mg of poloxamer 188 (BASF, Mount Olive, NJ) werε dissolved in 2 ml of hot methanol. Thε mεthanol was thεn evaporated to obtain a thin film of the phospholipid/stεroid mixture. The phosphohpid/steroid mixture was thεn dispersed in 64g of hot deionized water (T = 50 to 60°C) using an Ultra-Turrax mixer (model T 25) at 8000 rpm for 2 to 5 minutes (T = 60 70°C). 8g of perflubron (Atochem, Pans, France) was added dropwise during mixing. After the addition was complεtε, thε εmulsion was mixεd for an additional pεriod of not lεss than 4 minutεs Thε resulting coarse emulsion was then passed through a high pressurε homogεnizer (Avestiπ, Ottawa, Canada) at 18,000 psi for 5 passes. This emulsion was then usεd to form the feed stock which was spray dπεd as descπbεd above A freε flowing whitε powdεr was collected at the cyclone separator The hollow porous BDP particles had a tap density of lεss than 0.1 g/cm³.

VII Preparation of Hollow Porous Particles of TAA by Spray Drying Perforated microstructures comprising tπamcinolone acetomde (TAA) particles were prepared by a spray drying technique with a B 191 Mini Spray Drier (Buchi, Flawil, Switzerland) under thε following spray conditions- aspiration. 100%, inlet tεmpεrature. 85°C, outlεt tεmpεrature. 61 °C, fεεd pump 10%, N, flow. 2,800 L/hr. The fεεd stock was prepared by mixing 0 57g of lactose with a fluorocarbon in water emulsion immεdiatεly prior to spray drying. Thε emulsion was prepared by thε technique described below 100mg of TAA (Sigma, Chεmical Co., St. Louis, MO), 0.56g of EPC 100 3 (Lipoid KG, Ludwigshafεn, Gεrmany!, 25mg sodium oleate (Sigma), and 13mg of poloxamer 188 (BASF, Mount Olivε, NJ) were dissolved in 2 ml of hot methanol. The methanol was then evaporatεd to obtain a thin film of thε phosphohpid/steroid mixture. The phosphohpid/steroid mixture was then dispersed in 64g of hot deionized water (T - 50 to 60°C) using an Ultra-Turrax mixer (model T 25) at 8000 rpm for 2 to 5 minutes (T = 60 70° C). 8g of perflubron (Atochem, Pans,

France) was added dropwise during mixing. After the fluorocarbon was added, the emulsion was mixεd for at least 4 minutes. The resulting coarsε εmulsion was thεn passεd through a high pressure homogεmzεr (Avεstin, Ottawa. Canada) at 18,000 psi for 5 passεs. This εmulsion was than usεd to form thε feed stock which was spray dned as descπbed above. A free flowing white powder was collected at the cyclone separator. The hollow porous TAA particles had a tap density of less than 0.1 g/cm³.

Preparation of Hollow Porous Particles of ONasε I by Spray Drying Hollow porous DNase I particles were prepared by a spray drying technique with a B 191 Mini Spray- Drier (Buchi, Flawil, Switzerland! under thε following conditions: aspiration- 100%, inlet tempεrature: 80°C; outlet tempεraturε: 61 °C; fεed pump: 10%; N₂ flow: 2,800 L/hr. The feεd was prepared by mixing two solutions A and B immediatεly prior to spray drying.

Solution A: 20g of water was used to dissolve 0.5gr of human pancreas DNase I (Calbiochem, San Diego CA) and 0.012g of poloxamer 188 NF grade (BASF, Mount Olive, NJ). Solution B. A fluorocarboπ-iπ-water εmulsioπ stabilized by phospholipid was prepared in the following way. The phospholipid, 0.52g EPC 100 3 (Lipoid KG, Ludwigshafen, Gεrmanyl, was homogεnizεd in 87g of hot deionized water (T = 50 to 60°C) using an Ultra-Turrax mixer (model T 25) at 8000 rpm for 2 to 5 minutεs (T = 60-70°C). 13g of pεrflubron (Atochεm, Pans, France) was added dropwise during mixing. After the fluorocarbon was addεd, the εmulsion was mixεd for at lεast 4 minutes. The resulting coarse emulsion was then passεd through a high pressure homogenizer (Avestin, Ottawa, Canada) at 18,000 psi for 5 passεs.

Solutions A and B ware comb εd and fed into the spray dryer under the conditions descπbεd abovε. A free flowing pale yellow powder was collected at the cyclone separator. The hollow porous DNase I particles had a volume-weighted mean aerodynamic diametεr of 1.29 ± 1.40 μm as determinεd by a tιme-of-flιght analytical method (Aerosizεr, Amhεrst Process Instruments, Amherst, MA). Scanning elεctroπ microscopy (SEM) analysis showεd the powders to bε both hollow and porous. Thε tap dεπsity of thε powdεr was dεtεrminεd to be less than 0.1 g/cm³.

The foregoing examplε further illustrates the extraordinary compatibility of the presεnt invention with a variety of bioactivε agεnts. That is, in addition to relatively small hardy compounds such as steroids, the preparations of the present invention may be formulated to effectively incorporate larger, fragile moleculεs such as peptides, proteins and genetic mateπai.

IX Preparation of hollow porous powder by spray drying a gas in watεr emulsion

Thε following solutions wεrε prepared with watεr for injection Solution 1

3 9% w/v m HES hydroxyethylstarch (Ajinomoto, Tokyo, Japan) 3.25% w/v Sodium chloride (Malhnckrodt, St. Louis, MO)

2 83% w/v Sodium phosphate, dibasic (Malhnckrodt St Louis, MO)

0.42% w/v Sodium phosphate, monobasic (Malhnckrodt, St. Louis, MO)

Solution 2.

0 45% w/v Poloxamεr 188 (BASF, Mount Olivε, NJ)

1 35% w/v Hydrogεnatεd egg phosphatidylcholme, EPC 3

(Lipoid KG, Ludwigshafen, Gεrmany) The ingredients of solution 1 were dissolved in warm water using a stir plate. The surfactants in solution 2 were dispεrsεd in watεr using a high shεar mixer The solutions werε combined following εmulsification and saturatεd with mtrogεπ prior to spray drying.

Thε resulting dry, freε flowing, hollow, sphεπcal product had a mεan particle diamεter of 2 6 ± 1 5 μm The particles, which may be used for the replacεmεnt or augmentation of lung surfactant, were spherical and porous as detεrminεd by SEM

Thε previous εxample illustrates thε point that, a wide variety of blowing agents there nitroqen) may be used to provide microstructurεs exhibiting desirεd morphology Indεεd, one of the primary advantages of the present invention is the ability to alter formation conditions so as to presεrvε biological activity (i ε. with proteins or lung surfactant) or produce microstructurεs having selεctεd porosity

X

Preparation of Perforatεd Microstructure Powder Containing Ampicillin

Thε following matεπals wεre obtained and used to providε a feed stock

20% w/w Ampicillin, Biotech grade (Fisher Scientific, Pittsburgh, PA)

14 38% w/w Hydroxyethyl starch (Ajinomoto Japan)

65.62% w/w Dipalmitoylphosphatidylchohne (Genzyme, Cambridge, MA)

Pεrfluorohεxane (3M, St Paul, MN)

Deionized water Hydroxyethyi starch, (HES; 0.9 g), and dipalmitoylphosphatidylchohne (DPPC; 4 1 1 g) were dispersεd in 75 ml deionized water usinq an Ultra-Turrax mixer (modεl T-25) at 10,000 rpm for approximatεly 2 minutes (T = 45-50 C). The resulting DPPC/HES dispersion was chilled in an ice bath Ampicillin (1.25 g) was addεd and allowed to mix for 1 minute (T

= 5-10 C). Perfluorohexane (PFH, 4.1 1 g ) was then added dropwise during mixing (T = 5-10 0. After the addition was complεtε, the PFH in watεr εmulsion was mixεd on the Ultra Turrax for a total of not lεss than 4 minutεs.

A pεrforated microstructure powder comprising ampicillin was obtainεd by spray-drying (Buchi, 191 Mini Spray Dryer, Switzeriand) thε ampicillin containing εmulsion at a ratε of 5 5 ml/mm. The inlet and outlet tempεraturεs of the spray dryer were 90 C and 55 C respectively. The nebulization air and aspiration flows were 1,800 L/hr and 100% respectively. A free flowing white powdεr compπsing porous microspheres was obtained.

XI Effεct of Spray Drying on thε In Vitro Activity of Lung Surfactant Thε activity of a spray dried lung surfactant preparation to lower the surface tension of a pulsating bubble was compared with the neat lung surfactant preparation. Bovine derived lung surfactant, Alveofact (Thomae, Bibεrach, Gεrmany) and spray dπεd lung surfactant containing microshelis were dissolved in normal saline at a concentration of 10 mg/ml and allowed to incubate for 15 minutes at 37 C. Prior to analysis, the surfactant test solutions wεre vigorously shaken using a Vortex mixer for 30 seconds. The samples wεre analyzed for their surface properties using the Pulsating Bubble Surfactometer at 37 C (model EC PBS-B, Electronics, Amherst, NY) according to the manufacturers instructions. Surfactant solutions wεre allowεd to adsorb at minimum bubble diametεr for 10 seconds, and bubble cycling was performed in the automatic mode (20 cycles/minute). For each expeπment, mεasurεmεnts wεre takεn for approximatεly thε first 10 cyclεs, then again at t= 2, , and 6 minutes.

The main difference observed betwεen thε πεat and spray dried surfactant suspensions is thε rate at which they adsorb to the bubble surface and thus lower the tεnsion Thε spray dπεd materials required 6 cycles to achievε low surfacε tεnsion as compared with one cycle for thε Alveofact sample. However, the magnitude of thε tension at maximum, and minimum bubble diametεr wεre found to bε approximatεly thε samε.

For thε Alvεofact dispersion, the tension decreasεd from 32 mN/m at maximum diameter to 4 mN/m at minimum in the first cycle With further pulsation, a stεady state oscillation was reached with a maximum tension _max 33 mN/m and a minimum tension _nn 0 to 1 mN/m. For the spray-dned lung microshell dispersion, thε tεπsioπ dεcreased from 36 mN/m at maximum diametεr to 16 mN/m at minimum in thε first cycle. By the sixth pulsation, _ma, and _mm were respectively 36 and 2 mN/m. Both the neat Alvεofact and the spray dned lung surfactant pεrforatεd microstructures satisfy thε maximum and minimum surfacε tension requirεmεnts for physiologically effective lung surfactants as outlined by Notter; [R.H. Notter, in Surfactant Replacemεnt Therapy, (Eds: D.H. Shapiro, and R.H. Notter) Alan R. Liss, New York, 1989] these values should range from 35 to about 5 mN/m, respectively. This examplε illustrates that the compositions and methods of the present invention are particularly useful for the replacεmεnt or augmentation of lung surfactant in patients in need thereof.

XII

^ Preparation of Perforated Microstructure Powder Containing Insulin

The following materials were obtained and used to provide a feed stock.

0 0045% w/w Human Insulin, (CalBiochem, San Diεgo, CA) 17.96% wlw Hydroxyethyl starch (Ajinomoto, J apan) 82.04% w/w Dipalmitoylphosphatidylchohne (Genzymε, Cambndgε, MA) 1 0 Perfluorohεxanε (3M, St. Paul, MN)

Deionized water

Hydroxyethyl starch, (HES; 1 35 g) and dipalmitoylphosphatidylchohne (DPPC; 6.16 g) were dispersed in 100 ml deionized water using an Ultra Turrax mixer (model T 25) at 10,000 rpm for approximately 2 minutes (T = 45-50 C). Thε resulting DPPC/HES dispersion was then chilled in a ice bath. Insulin (3.4 mg) was addεd and allowεd to mix for 1 minutε

I 5 (T = 5 10 C). Perfluorohεxaπe (PFH 6.16 g) was then addεd dropwisε during mixing (T = 5 10 C). Aftεr thε addition was complete, the resulting PFH in water emulsion was mixed with the Ultra Turrax) for a total of not less than 4 minutes. The insulin microstructure powder was obtained using a Buchi model 191 mini spray dryer (Buchi, Switzerland). The insulin containing emulsion was fed at a rate of 5 5 ml/mm. Thε inlet and outlet temperatures of the spray dryer were 80 C and 45 C respectively. The nebulization air and aspiration flows wεre 1 ,800 L/hr and 100% respectively. A 0 free flowing, white powder compπsing porous microspheres was obtained

XIII

Effect of Pεrflubron on thε In Vitro Activity of DNAse I Bovine pancreas deoxynbonucleasε I, (DNAse I Calbiochεm, San Diego, CA) was dispersed in perflubron ( 1 5 mg/ml) and allowed to incubate for 1 hour. The perflubron was then evaporated using a Savant Speεd Vac (Farmingdalε,

NY) Thε activity of thε pεrflubron treated DNAse I to cleavε the phosphodiεster linkages of DNA was compared with an untreated DNAse preparation. Seπal dilutions of a DNAse solution (1 mg/ml) was combined with 50 g DNA and dissolved in 500 L of a 10mM Tns HCI buffer (6.3 pH) which contained 0 15 mg/ml CaCl, and 8 77 mg/ml NaCI The samples were placed on an orbital shaker and incubated at 37 C for 30 minutes. The condition of the DNA in each sample after 0 incubation was then exammεd εlεctrophoretically over a 1 % agarose gei which contained ethidium bromidε for visualization. No difference in DNA cleavage was observed betwεεπ thε untreated and perflubron treated DNAse I samplεs

XIV The Preparation of DNAsε Microdispersion in Perflubron One milhliter of the following solution was prepared. 0 00001 %, w/v, Bovine pancreas deoxyπbonuclεase I, (DNAse I) (Calbiochem, San Diεgo, CA) and 0.001 % polyvinyl pyrrolidonε (PVP) (Sigma, St Louis, MO), was dissolvεd into a solution composed of 0.121 %, w/v, tπsltiydroxymethyl) aminomethane (Sigma), 0.0000015 %, w/v, CaCl, 2H20 (Sigma) and 0 0000877% w/v, NaCI (Sigma) The pH of thε solution was adjustεd to 6 3 pnor to adding thε DNAsε or PVP

Oπε hundred microhters of the DNAse/PVP solution was added to a 12x100 mm test tubε containing 5 ml pεrfiuorooctylethane (F Tεch, Japan) Thε tubε was capped and submerged in a sonicator bath (Branson Model 3200, Daπbury, CT) for 5 seconds to obtain a milky dispersion in the perflubron The suspension was then evaporated to dryness using a Savant Speed Vac (Model SC 200) The resulting dned microsphεrεs wεre rεsuspεndεd with 7 ml Perflubron A milky DNAse/PVP in perflubron suspension was obtained Particle size analysis was done by laser diffraction (Hoπba LA 700, Irvine, CA) in the volume weighted mode Approximately a 20 to 50 L aliquot of each sample was diluted in 9 to 10 ml of π dodεcaπe. The distribution shape "3", refractive index ratio of 1 1 and the fraction cell was used The resulting microdispersion had a mean droplet diametεr of 2 83 m Examplεs XIII and XIV clearly demonstrate the feasibility of preparing enzymatically active stabilized dispersions in accordance with the present invention This Example further illustrates that a numbεr of tεchniquεs may bε usεd to form compatible particulates useful in the disclosed dispersions

XV

Preparation of Fluorescεnt Labeled Perforated Microstructure Powdεr via Spray Drying

The following mateπals wεre obtained and used to manufacture fεεd stock

0 2% w/w Nitrobεnzoyldiol Phosphatidylcholme (Avanti Polar Lipids, Alabaster, AL)

17 6% w/w Hydroxyethyl starch (Ajinomoto Japan) 82.2% w/w Dipalmitoylphosphatidylchohne (Genzyme, Cambridge, MA) Perfluorohexane (3M, St Paul, MN)

Deionized watεr

Dipalmitoylphosphatidylchohne (DPPC, 1 g) and nitrobeπzoyldiol phosphatidylcholme (NBD PC, 10 mg) were dissolved in 4 ml chloroform The chloroform was thεn removed using a Savant Speεd Vac (Modεl SC 200)

Hydroxyethyl starch, (HES, 0 9 g), dipalmitoylphosphatidyl choline (DPPC, 3 19 g) and 75 ml deionized watεr were then added to the DPPC/NBD PC thin film The surfactants and starch werε thεn dispεrsεd in thε aqueous phase using an

Ultra Turrax mixer (model T 25) at 10,000 rpm for approximately 2 minutes (T = 45 50 C) The resulting NBD

PC/DPPC/HES dispersion was chilled in an ice bath Pεrfluorohεxanε (PFH 4 1 1 g ) was thεn addεd dropwise during mixing (T = 5 10 C) Aftεr the addition was complete, the resulting PFH in water emulsion was mixεd on the Ultra Turrax for an additional time of not lεss than 4 minutεs Thε fluorεscεntly labeled microshell powdεr was obtainεd by spray drying (Buchi, 191 Mini Spray Dryεr, Switzεrland). Thε NBD PC/DPPC/HES containing emulsion was fed at a rate of 5.5 ml/mm. The inlet and outlet tempεraturεs of the spray dryer were 100 C and 65 C respectively. The nebulization air and aspiration flows were 1 ,800 L/hr and 100% respectively A free flowing, yellow powdεr comprising pεrforatεd microstructures was obtained.

XVI Inhalation Behavior of a Perforated Microstructure In Fluorocarbon Dispersion vs. Agueous Liposomes The nebulization profile as a function of the aerodynamic diameter of a spray dried microshεll in perflubron dispersion vs. an aqueous based hposomal dispersion was evaluated using an Andersen Cascade Impactor. For the experiments, compressεd air served as the earner and aerosol gεπεrating gas An air flow ratε of 7 5 htεrs/min was established at a pressure of 20 p.s.i. Aerosols were generated with a DeVilbiss air jet nebulizer (DeVilbiss Co., Somerset, PA). Thε nebulizer was connected to an Andersεn cascadε impactor (Siεrra Andersεn 1 ACFM Nonviable Ambient Particle Sizing Sampler). The aqueous hposomal dispersion was preparεd by dispersing fluorescent labeled microshells prepared as sεt forth in Examplε XIV in watεr, followed by sonification with a Vibraceil sonicator (Sonics Matεπals, 30 mm o.d titanium probe) at a power of 100 watts for approximately 2 minutes (T= 22 25 C). The samε pεrforated microstructures were suspended in PFOB to provide a stabilized dispersion. 5 ml of either a 20 mg/ml fluorεscεntly labeled microshell in PFOB dispersion or the aqueous fluoresceπtly labeled liposomes wεre nebulized for 4 minutes. The 8 stagεs of the impactor were then washεd with chlorofomrmεthanol (2:1 v/v) Each stagε εxtract was thεn transferred to a 2 milhliter volumεtπc flask and q.s. to thε mark with chlorofoπτt:methaπol (2.1 v/v).

The extracts werε measured for fluorescεncε content using the following conditions- _9X =■ 481 nm , _m = 528 nm and quantified by comparison to an external standard curve. Table III lists the characteristics of each cascadε impactor stagε, thε inhalation behavior of the nebulized microshells and liposomes The NBD PC mass distribution as a function of aerodynamic diameter was calculated using calibration curvεs described by Gonda, et. al., [Goπda, I., Kayes, J.B., Groom, C.V., and Ftldes, F.J.T ; Characterization of hydroscopic inhalation aerosols In Particle Size Analysis 1981

(Eds. N.G. Stanlet Wood, and T. Allen), pp. 31 43, Wiley Heydεn Ltd, New York] and incorporated herein by reference.

Compaπson of the two delivery vehicles revealed that the efficiency of nebulization was grεatεr for thε posomεs. On thε othεr hand, a higher percεntagε of thε nebulized dose to smaller airway diameters could be achievεd with thε fluorocarbon dεhvεrεd microstructurεs, which is reflection of it's smaller median mass aerodynamic diametεr (MMAD), achieved due its hollow, porous nature. This Examplε and thε results shown in Table III immediately bεlow clearly illustrate that a number of different colloidal systems, including both particulate dispersions and hposomal preparations, are compatible with the presεnt invention. Table III

Median Mass Aerodynamic Diameters of Hollow Microspheres vs. Liposomes

XVII

Andersεn Impactor Test for Assessing Aεrosol Performance

Formulations described in Examples XVIII, XIX, XX and XXI comprising Cromolyn sodium were tested using commonly accepted pharmaceutical procεdurεs. The method utilized was compliant with the United State

Pharmacopeia (USP) procedure (Pharmacopeial Prεviεws (1996) 22.3065-3098) incorporated herein by reference. The Andersen Impactor was associated with thε respective nebulizer or metεrεd dosε inhaler as set forth in thε following εxampiεs and collected aerosolized sample for a specified period.

Extraction procedure Thε εxtraction from all thε piatεs, induction port, and actuator wεre pεrformεd in closed vials with 10 L of a suitable solvent. The filter was installed but not assayed, because the polyacrylic binder mtεrfεrεd with thε analysis The mass balance and particle sizε distribution trends indicated that thε dεposition on thε filter was negligibly small. Thε piatεs wεrε εxtractεd with deionized water.

Quantitation procedure Cromolyn sodium was quantitated by absorption spεctroscopy (Beckman DU640 spectrophotomεter! relative to an external standard curve with the extraction solvent as the blank. Cromolyn sodium was quantitated using the absorption peak at 326 nm

Calculation procedure. For each formulation, the mass of the drug in the device as well as on thε induction port ( 1 ) and piatεs (0 7) wεre quantified as described above. The Fine Particle Dosε and Finε Particle

Fraction was calculated according to the USP method refεrenced above. Throat deposition was defined as the mass of drug found in the induction port and on plates 0 and 1. Thε mεaπ mass aerodynamic diameters (MMAD) and geometric standard diameters (GSD) wεre evaluated by fitting the experimental cumulative function with log normal distribution by using two pararnεtεr fitting routine The results of such mεasurεments are presented in subsequent examples.

XVlll Nebulization of Porous Particulate Structures Comprising Phospholipids and Cromolyn sodium in Perfluorooctylethanε using a MicroMist Nebulizer Forty milligrams of the hpid based microspheres containing 50% cromolyn sodium by weight (as from Example V) wεre dispersed in 10 ml perfluorooctylethane (PFOE) by shaking, forming a suspension. The suspension was πebuhzεd until thε fluorocarbon liquid was delivered or had evaporatεd using a Micro Mist (DεVilbiss) disposable nebulizer using a PulmoAide^' air compressor (DeVilbiss). As described above an Andersen Cascade Impactor was used to measure the resulting particle size distnbution. The impactor was disassembled and the piatεs of thε impactor wεre extracted with water. Cromolyn sodium content was measured by UV adsorption at 326nm. The fine particle fraction is the ratio of particles depositεd in stagεs 2 through 7 to those depositεd in all stagεs of thε impactor Thε fine particle mass is the weight of mateπai depositεd in stages 2 through 7 The deep lung fraction is the ratio of particles deposited in stages 5 through 7 of the impactor (which correlate to the alveoli) to those deposited in all stages The deεp lung mass is thε weight of matεπal deposited in stages 5 through 7. Table IV immediately below provides a summary of the results.

Table IV

XIX Nebulization of Porous Particulate Structures Comprising Phospholipids and Cromolyn Sodium in Perfiuorooctyiεthane using a Raindrop Nebulizer A quantity of hpid based microspheres containing 50% cromolyn sodium, as from Example V, weighing 40 g was dispersεd in 10 ml perfluorooctylethane (PFOE) by shaking, thereby forming a suspension. The suspension was nebulized until thε fluorocarbon liquid was delivered or had evaporated using a Raindrop disposable nebulizer (Nellcor Puπtan Bennet) connected to a PulmoAide air compressor (DeVilbiss) An Andersen Cascade Impactor was used to measure the resulting particle size distnbution in the manner described in Examples XVII and XVlll Table V immεdiatεiy bεlow provides a summary of the results. Table V

XX Nebulization of Agueous Cromolyn Sodium Solution The contents of plastic vial containing a unit dose inhalation solution of 20 mg of cromolyn sodium in 2 ml purified water (Dey Laboratories) was nebulized using a Micro Mist disposable nebulizer (DeVilbiss) using a PulmoAide® air compressor (DeVilbiss). The cromolyn sodium solution was nebulized for 30 minutes. An Andersen Cascade Impactor was used to measure the resulting particle size distribution, by the method described above in Example XVII. Table VI im ediatεly bεlow providεs a summary of the results. In this regard, it will be appreciated that, thε formulations nebulized from fluorocarbon suspension mediums in Examples XVlll and XIX provided a greater percεntage of deεp lung dεposition than the aqueous solution.

Table VI

XXI Preparation of a Mεtεrεd Dosε Inhaler of Cromolyn Sodium A pre-wεighεd amount of hollow porous cromolyn sodium particles prepared in Examplε V was placεd into a 10 ml aluminum can and driεd in a vacuum oven undεr thε flow of nitrogen for 3-4 hours at 40°C. The amount of powder filled into the can was detεrminεd by thε amount of drug required to provide a desirεd thεrapεutic effect. After this the can was crimp-sealed using a DF31 /50act 50μl valve (Valois of America, Greεnwich, CT) and filled with HFA-134a propellant (DuPont, Wilmington DE) by overpressure through the stem. Thε amount of propεllant in thε can was determined by weighing the can before and after the fill.

The filled MDI was then used to compare the administration of cromolyn sodium using a metεrεd dosε inhalεr and a nεubulizer. More specifically, a cromolyn sodium preparation was nebulized and quantitated as describεd in Example XVIII. The MDI was thεπ associated with thε Andεrsεn impactor and discharged. For the test, 5 shots were sent to waste and, 20 shots were made into the Andersen impactor. A compaπson of the Andersen cascade impactor results for thε nebulized cromolyn sodium and the cromolyn sodium administered by the MDI is shown in Fig. 3. As seen in the Figure, a significantly greater percentage of the nebulized drug is found on plates 5 7 showing the enhanced potential for systemic delivery via nebulization

XXII

Nebulization of Porous Particulate Structures Comprising Mixtures of Long Cham/Short Chain Phospholipids and Albuterol Sulfatε in Pεrflubron To further demonstrate the diversity of the present invention the spray dried powder from Example IV was dispersed in perflubron (Atochem, France) at 0.2 wt% concentration. The resulting stabilized dispersion did not show any visible sedimentation over 30 minutes and could be easily nebulized with a Pulmo-Neb Disposable Nebulizer (DeVilbiss,

Somerset, PA). A significant deposition of the powder was found on plates 4 and 5 of an Andersen cascade impactor, as judged by visual inspection, indicating that significant deposition is likely in human secondary and terminal bronchi.

Those skilled in thε art will further appreciate that the present invention may be embodiεd in other specific forms without departing from the spiπt or central attributes thereof In that the foregoing descnption of the prεsεnt invention discloses only exemplary embodiments thereof, it is to be understood that, other vaπations are contemplatεd as being within thε scopε of thε present invention. Accordingly, the present invention is not limited to the particular embodiments which have been descπbed in detail herein. Rather, reference should be made to the appended claims as indicative of the scope and content of thε invention.

Claims

WHAT IS CLAIMED:

I Use of a liquid fluorochemical in the manufacture of a medicament for the pulmonary delivery of a bioactive agent whereby the medicament compnses a stabilized dispersion having a fluorochemical continuous phase which is nebulized using a nebulizer to form an aerosolized medicam╬╡nt comprising said bioactiv╬╡ ag╬╡nt wherein said aerosolized medicament is in a form for administration to at least a portion of the pulmonary air passag╬╡s of a patient in need thereof

2. The use of claim 1 wherein said stabilized dispersion compnses a revers╬╡ ╬╡mulsion, micro╬╡mulsio╧Ç or a particulate dispersion

3. The use of claim 1 wherein said stabilized dispersion compnses a plurality of particulates suspended in said fluorochemical continuous phase wherein said particulates are s╬╡l╬╡cted from the group consisting of micronized particles, nanocrystals, spray dned microspheres, perforated microstructures and combinations thereof.

4 The us╬╡ of claim 1 wh╬╡rei╧Ç said stabilized dispersion compnses a plurality of perforat╬╡d microstructur╬╡s suspended in said fluorochemical continuous phase

5. The use of claim 4 wherein said perforated microstructur╬╡s compnse a surfactant

6. The use of claim 5 wherein said surfactant is selected from the group consisting of phospholipids, nonionic det╬╡rgents, nonionic block copolymers, ionic surfactants, biocompatible fluorinated surfactants and combinations thereof.

7 The us╬╡ of claims 5 or 6 wherein said surfactant is a phospholipid

8. The use of claim 7 wherein said phospholipid is sel╬╡cted from the group consisting of dilauroylphosphatidylcholine, dioleylphosphatidylchohne, dipalmitoylphosphatidylcholine, disteroylphosphatidylcholine, behenoylphosphatidyl choline, arachidoylphosphatidylchohne and combinations thereof

9. The use of claims 4 to 8 wherein the mean a╬╡rody╧Çamic diameter of the p╬╡rforated microstructur╬╡s is between 0.5 and 5 ╬╝m

10. The use of any of claims 1 to 9 wherein said bioactive agent is selected from the group consisting of antiallergics, bronchodilators, pulmonary lung surfactants, analgesics antibiotics, leukotnene inhibitors or antagonists, antihistamines, antnnflammato╧Çes, antineoplastics, anticholmergics, anesthetics, anti tuberculars, imaging agents, cardiovascular agents, enzymes, steroids, gen╬╡tic mate╧Çai, viral vectors, antisens╬╡ ag╬╡nts, proteins, peptid╬╡s and combinations thereof.

I I The use of any of claims 1 to 10 wher╬╡in said bioactiv╬╡ ag╬╡nt is delivered to th╬╡ systemic circulation of said patient.

12. A method for forming a stabilized respiratory dispersion comp╧Çsing the steps of combining a plurality of perforated microstructures compnsing at least one bioactive ag╬╡nt with a predetermined volume of a nonaqueous suspension medium to provide a respiratory blend wherein said suspension m╬╡dium p╬╡rm╬╡at╬╡s said p╬╡rforat╬╡d microstructur╬╡s; and mixing said respiratory blend to provide a substantially homogeneous respiratory dispersion.

13. The method of claim 12 wher╬╡in said perforated microstructures comprise a surfactant

14. The method of claim 13 wherein said surfactant is selected from the group consisting of phospholipids, nonionic det╬╡rg╬╡nts, nonionic block copolymers, ionic surfactants, biocompatible fluorinated surfactants and combinations thereof.

15. The method of claim 13 or 14 wherein said surfactant is a phospholipid.

16. The method of claim 15 wherein said phospholipid is selected from the group consisting of dilauroylphosphatidylcholine, dioleylphosphatidylchohne, dipalmitoylphosphatidylchohne, disteroylphosphatidylcholine behe╧Çoylphosphatidylchohne, arachidoylphosphatidylchohne and combinations thereof

17. The method of any of claims 12 to 16 wherein said suspension medium and said perforated microstructures have a refractive index differential of less than about 0.5.

18. The method of any of claims 12 to 17 wherein said perforated microstructures compose hollow porous microspher╬╡s.

19. The method of any of claims 12 to 18 wherein the mean aerodynamic diameter of said perforated microstructur╬╡s is b╬╡tw╬╡╬╡n 0 5 and 5 ╬╝m.

20. The method of any of claims 12 to 19 wherein said bioactive agent is sel╬╡ct╬╡d from th╬╡ group consisting of antiallergics, bronchodilators, pulmonary lung surfactants, analgesics, antibiotics, leukotnene inhibitors or antagonists, antihistamines, antnnflammatories, antineoplastics, anticholmergics, a╧Ç╬╡sth╬╡tics, anti tuberculars, imaging agents, cardiovascular agents, enzymes, steroids, genetic matenal, viral v╬╡ctors, antis╬╡ns╬╡ ag╬╡nts, prot╬╡ins, peptides and combinations thereof.

21. A method for stabilizing a respiratory dispersion by reducing attractive van der Waals forces compnsing the steps of. providing a plurality of perforat╬╡d microstructures; combining th╬╡ p╬╡rforat╬╡d microstructures with a susp╬╡╧Çsion medium comprising at l╬╡ast on╬╡ fluorochemical wher╬╡in th╬╡ susp╬╡nsion m╬╡dium and th╬╡ p╬╡rforat╬╡d microstructures are sel╬╡ct╬╡d to provid╬╡ a r╬╡fractiv╬╡ index differential value of less than about 0.5.

22. The method of claim 21 wher╬╡in said perforat╬╡d microstructur╬╡s comp╧Çs╬╡ a surfactant

23. The method of claim 22 wherein said surfactant is select╬╡d from the group consisting of phospholipids, nonionic detergents, nonionic block copolymers, ionic surfactants, biocompatible fluorinated surfactants and combinations thereof.

24. The method of claim 22 or 23 wherein said surfactant is a phospholipid.

25. Th╬╡ method of claim 24 wher╬╡in said phospholipid is s╬╡l╬╡cted from the group consisting of dilauroylphosphatidylcholine, dioleylphosphatidylchohne, dipalmitoylphosphatidylchohne, disteroylphosphatidylcholine beh╬╡noylphosphatidylchohn╬╡, arachidoylphosphatidylchohne and combinations thereof.

26. The method of any of claims 21 to 25 wherein said perforat╬╡d microstructur╬╡s compnse hollow porous microspheres.

27. The method of any of claims 21 to 26 wherein said bioactive agent is selected from the group consisting of antiallergics, bronchodilators, pulmonary lung surfactants, analgesics, antibiotics, leukotnene inhibitors or antagonists, antihistamines, antnnflammatories, antineoplastics, anticholmergics, anesthetics, anti tuberculars, imaging agents, cardiovascular agents, enzymes, steroids, genetic matenal, viral vectors, antisense agents, proteins, peptides and combinations thereof

28. A stable respiratory dispersion for use in a nebulizer composing a suspension medium having dispersed therein a plurality of perforated microstructures comp╧Çsing at least one bioactive agent wh╬╡rein said suspension m╬╡dium substantially p╬╡rmeates said perforated microstructures.

29. The dispersion of claim 28 wh╬╡rein said p╬╡rforat╬╡d microstructur╬╡s comp╧Çs╬╡ a surfactant

30. Th╬╡ dispersion of claim 29 wh╬╡rein said surfactant is sel╬╡cted from the group consisting of phospholipids, nonionic det╬╡rg╬╡nts, nonionic block copolymers, ionic surfactants, biocompatible fluorinated surfactants and combinations thereof.

31. The dispersion of claim 29 or 30 wherein said surfactant is a phospholipid

32. The dispersion of claim 31 wherein said phospholipid is select╬╡d from th╬╡ group consisting of dilauroylphosphatidylcholine, dioleylphosphatidylchohne, dipalmitoylphosphatidylchohne, disteroylphosphatidylcholine behe╧Çoylphosphatidylchoh╧Çe, arachidoylphosphatidylchohne and combinations thereof.

33. The dispersion of any of claims 28 to 32 wh╬╡rein said suspension m╬╡dium and said perforated microstructures have a refractive index differential of l╬╡ss than about 0 4

34. The dispersion of any of claims 28 to 33 wher╬╡in said perforated microstructures cornp╧Çs╬╡ hollow porous microsph╬╡res

35. The dispersion of any of claims 28 to 34 wherein the mean aerodynamic diamet╬╡r of said p╬╡rforated microstructur╬╡s is b╬╡tw╬╡╬╡n 0 5 and ╬╝m.

36. The method of any of claims 28 to 35 wherein said bioactive ag╬╡nt is selected from th╬╡ group consisting of antiallergics, bronchodilators, pulmonary lung surfactants, analgesics, antibiotics, leukotnene inhibitors or antagonists, antihistamines, antnnflammatories, antineoplastics, anticholmergics, anesth╬╡tics, anti tub╬╡rculars, imaging agents, cardiovascular agents, enzymes, steroids, genetic matenal, viral vectors, antisense agents, proteins, peptides and combinations thereof.

37. An inhalation system for the pulmonary administration of a bioactive agent to a patient comp╧Çsing. a fluid reservoir; a stable respiratory dispersion in said fluid reservoir wherein said stabilized dispersion compnses a fluorochemical continuous phase and at least one bioactive agent; and a nebulizer operabiy associated with said fluid reservoir wherein the nebulizer is capable of aerosolizing and discharging the stable respiratory dispersion.

38. The system of claim 37 wherein said stabilized dispersion compnses a reverse emulsion, microemulsion or a particulate dispersion.

39. The system of claim 37 wherein said stabilized dispersion comprises a plurality of particulates suspended in said fluorochemical continuous phase wher╬╡in said particulates are selected from the group consisting of micronized particles, na╧Çocrystals, spray dned microspheres, perforated microstructures and combinations thereof.

40. The syst╬╡m of claim 37 wh╬╡r╬╡in said stabilized dispersion comprises a plurality of perforated microstructures suspended in said fluorochemical continuous phase

41. The system of claim 40 wherein said perforated microstructures comp╧Çs╬╡ a surfactant.

42. The system of claim 41 wherein said surfactant is selected from the group consisting of phospholipids, nonionic det╬╡rg╬╡nts, nonionic block copolymers, ionic surfactants, biocompatible fluorinated surfactants and combinations thereof.

43 The system of claims 41 or 42 wher╬╡in said surfactant is a phospholipid.

44. The system of claim 43 wherein said phospholipid is selected from the group consisting of dilauroylphosphatidylcholine, dioleylphosphatidylchohne, dipalmitoylphosphatidylchohne, disteroylphosphatidylcholine, behenoylphosphatidyl choline, arachidoylphosphatidylchohne and combinations thereof.

45. The system of any of claims 40 to 44 wher╬╡in the m╬╡a╧Ç aerodynamic diameter of the perforat╬╡d microstructures is between 0 5 and 5 ╬╝m.

46. The system of any of claims 37 to 45 wherein said bioactive agent is selected from the group consisting of antiallergics, bronchodilators, pulmonary lung surfactants, analgesics, antibiotics, leukotnene inhibitors or antagonists, antihistamines, a╧Çtii╧Çflammato╧Çes, antineoplastics, anticholmergics, anesthetics, anti tuberculars, imaging agents, cardiovascular agents, enzymes, steroids, genetic mate╧Çai, viral v╬╡ctors, antis╬╡ns╬╡ agents, proteins, peptides and combinations thereof.

47 The system of any of claims 37 to 46 wherein said bioactive agent comp╧Çs╬╡s a compound s╬╡lected from the group consisting of proteins, peptides and genetic material.

48. The system of any of claims 37 to 47 wherein said fluid reservoir is a multi dose res╬╡rvoir or a single dose reservoir.

49. The system of any of claims 37 to 48 wherein said nebulizer is a jet nebulizer, an ultrasonic nebulizer or a single-bolus nebulizer.

50. A method for the pulmonary delivery of one or more bioactive agents comp╧Çsing the steps of: providing a stabilized respiratory dispersion comp╧Çsing one or more bioactive agents wherein the respiratory dispersion compnses a fluorochemical continuous phase; nebulizing said respiratory dispersion with a nebulizer to provide an aerosolized medicament; and administ╬╡╧Çng a therap╬╡utically effective amount of said aerosolized medicament to at l╬╡ast a portion of the pulmonary passages of a patient in need thereof.