WO2002038183A2

WO2002038183A2 - Delivery devices

Info

Publication number: WO2002038183A2
Application number: PCT/GB2001/004982
Authority: WO
Inventors: Ruth Elizabeth Cameron; Kirsten Joanne Dickers; Georgina Emily Milroy; Hiep Huatan
Original assignee: Cambridge University Technical Services Limited
Priority date: 2000-11-10
Filing date: 2001-11-09
Publication date: 2002-05-16
Also published as: WO2002038183A3; AU2002212551A1

Abstract

A process is provided for impregnating a substantial homopolymer of glycolic acid selected form substantial homopolymers of glycolic acid and block copolymers comprising at least 40 mol. % glycolic acid monomer as blocks which are substantial homopolymers of glycolic acid with a pharmaceutically active compound, the process comprising dissolving the pharmaceutically active compound in a solvent to form a solution of pharmaceutically active compound, contacting the solution with the polymer and allowing the solution to penetrate the polymer, characterised in that the solvent is liquid at atmospheric pressure and 20 °C and is capable of penetrating the polymer and is not capable of dissolving the polymer. The solvent may be for instance water or an organic solvent having solubility parameter S of from 18.5 to 28.0 Mpa1/2. The product may be used for implantation in a human or other animal subject. Also provided is a product suitable for implantation in the body of a human or other animal subject comprising a pharmaceutically active compound encapsulated by a casing which forms a barrier between the pharmaceutically active compound and the environment, wherein at least part of the barrier is formed from a membrane of glycolic acid polymer selected from substantial homopolymers of glycolic acid and block copolymers comprising at least 40 mol. % glycolic acid monomer as blocks which are substantial homopolymers of glycolic acid.

Description

DELIVERY DEVICES

The present invention relates to delivery devices for materials such as drugs based upon the biodegradable polymer, polyglycolide. In particular it relates to processes for the production of polyglycolide impregnated with pharmaceutically active compounds. It also relates to methods of use of such products and further to novel implants based upon polyglycolide.

It is known to provide, as drug delivery devices, implants which can be placed in the body of a human or other animal subject, the implants being formed from biodegradable polymer containing drug. The drug is released into the body from the delivery device over a period of time. Various polymers are known to be suitable in this area and include polymers of lactic acid and glycolic acid. These can be polylactide (substantial homopolymer of lactic acid) , polyglycolide (substantial homopolymer of glycolic acid) or poly (lactide-co- glycolide) (copolymer of lactic acid and glycolic acid) . Also known are block copolymers containing blocks of glycolide homopolymer, as disclosed in for example US 4,429,080. Sutures formed from polyglycolide homopolymer are disclosed in US 3,297,033.

US 3,896,813 and US 4,024,871 each discuss sutures impregnated with antimicrobial agents. Sutures formed from silk and polyethylene terephthalate having antimicrobials impregnated therein are disclosed in US 3,896,813. US 4,024,871 discloses a variety of suture materials including homopolymers and copolymers of hydroxy carboxylic acid esters in general. The exemplified sutures are based on

"polyester" and coated with polyurethane . They are impregnated with antimicrobial .

Polyglycolide is suitable for use in forming implants because it exhibits convenient degradation time and is non- toxic, biocompatible and degrades to inert products which make it suitable for use in both human and veterinary medicine. However, hitherto use of polyglycolide has been limited due to problems with processing polyglycolide to provide suitable implants.

Known techniques for incorporating drugs in biodegradable polymers include processes in which the polymer is melted. However, polyglycolide has a melting temperature of above 200°C, at which many drugs are decomposed or degraded.

Other techniques involve dissolution of the polymer in an organic solvent (in some cases, the drug is also in solution in the solvent) . However, polyglycolide dissolves in very few solvents. These include hexafluoroisopropanol

(HFIP) , hexafluoroacetone sesquihydrate and phenol- trichlorophenol . No solvent for polyglycolide is physiologically acceptable and thus their use is restricted.

US 3,297,033 generally discusses the inclusion of "other substances", such as dyes, antibiotics, .antiseptics, anaethestics and antioxidant in sutures but it is unclear whether these are added during polymerisation or after polymerisation. No methods of impregnation are given or exemplified. US 4,429,080 generally mentions polymers containing dispersed drug for continuous administration but again no methods for obtaining this are disclosed or exemplified. Consequently, use of biodegradable polymer based drug delivery devices has previously focused upon other polymers such as polylactide and poly (lactide-co-glycolide) .

However, it would be desirable to provide convenient and physiologically acceptable systems which enable drugs to be incorporated into polyglycolide.

Systems using HFIP or hexafluoroacetone sesquihydrate are described by Kost, J. et al (1988) Macromol . Symposia 19, 275-285 and Sato T. et al (1988) Pharm. Res. 5(1), 21- 30. Other groups have described impregnation of polymers including polyglycolide by supercritical carbon dioxide. See for instance US 5,508,060. However, we have found this system to be inconvenient because it requires the production of supercritical fluid. inckler, S. et al (1992) Langenbecks . Arch. Chir. 377, 112-117 and Overbeck J. P. et al (1995) J. Invest. Surg. 8, 155-162 describe impregnation of polyglycolide Dexon fibres with ciprofloxacin. The solvent for ciprofloxacin is not stated but the statements of solution concentration would indicate that it is not an aqueous solution. The system described also involves melting of the polymer at temperatures of from 180 to 220°C after impregnation. It is unclear whether the solution impregnates the Dexon sutures to any extent before melting takes place.

It is known to provide reservoir devices such as the intrauterine contraceptive device Progestasert (trade name, product supplied by Alza) . This consists of a progesterone core surrounded by a cylindrical non-biodegradable polymer membrane. This releases about 60 micrograms drug per day for one year and is then replaced. Norplant (trade name, product supplied by yeth-Ayerst) is another contraceptive implant, consisting of levonorgestrel-filled inert polymer capsules. These are implanted into the upper arm, so that steroid is administered continuously for up to five years. Glaucoma can be controlled by the Ocusert (trade name, product supplied by Alza) device, which is placed under the eyelid. The device, which has a pilocarpine core between two polymer membranes, releases drug for one week and can then be replaced. These systems are non-resorbable . The product Capronor (trade name) is a capsule formed from polycaprolactone and contains the contraceptive steroid levonorgestrel . It releases drug for about one year and is completely degraded by the end of three years . Each of these types of reservoir system exhibits a release profile in which the drug is released continuously and steadily over a period of time. It would be desirable to be able to provide a reservoir device which is capable of providing a different release profile, in particular a profile such that initial release of drug is low or negligible for a period of time, followed by a rapid release of a relatively large dose of the required drug.

According to a first aspect of the invention we provide a process for impregnating a polymer of glycolic acid selected from substantial homopolymers of glycolic acid and block copolymers comprising at least 40 mol . % glycolic acid monomer as blocks which are substantial homopolymers of glycolic acid with a pharmaceutically active compound, the process comprising dissolving the pharmaceutically active compound in a solvent to form a solution of pharmaceutically active compound, contacting the solution with the polymer and allowing the solution to penetrate the polymer, characterised in that the solvent is liquid at 20°C at atmospheric pressure and is capable of penetrating the polymer and is not capable of dissolving the polymer.

Contrary to previous assumptions we find that good impregnation can be achieved by the use of a solvent which is not capable of dissolving the polymer of glycolic acid. Furthermore, it is not necessary to use supercritical fluids and to encounter the attendant problems.

The polymer impregnated is preferably a substantial homopolymer of glycolic acid. By "substantial homopolymer" we mean that substantially all of the monomers are glycolic acid monomers. A low amount (up to 5%) of other monomers such as lactic acid may be included but preferably the amount of other monomers is not more than 3%, preferably not more than 1% (by weight based on monomer mixture) .

Particularly preferably the polymer is formed from 100% glycolic acid monomer.

The polymer impregnated can be a block copolymer having blocks which are substantial homopolymers of glycolic acid. Preferably at least 40 mol . % of the block copolymer is formed of such blocks, more preferably at least 50%, in particular at least 55%. These polymers will be referred to below as polyglycolides .

Generally the monomers are underivatised glycolic acid. Derivatives of glycolic acid may also be used if appropriate but preferably the monomers are underivatised glycolic acid.

The homopolymer is impregnated with an additive. This may be any suitable compound, for example therapeutically active agents and nutritional compounds for both human and veterinary use; or others such as fragrances, pesticides and biocides, etc., wherein the polymer as described in this invention could function as a carrier to control the release of the said agents.

Suitable therapeutically active agents are those which alter the physiological function of the target species in a beneficial or therapeutic manner. These agents are well described in the art and can be categorised according to their chemical classes such as inorganic molecules, organic heterocycles and macromolecules, for example, proteins and peptides.

The therapeutic agents as described in the above chemical classes have utility in the treatment of medical conditions, for example in the following categories: (1) gastrointestinal dysfunction, (2) cardiovascular diseases, (3) respiratory diseases, (4) central and peripheral nervous system diseases, (5) infective disorders, (6) inflammatory disorders, (7) oncology diseases, (8) endocrine diseases, (9) anaesthetic therapy and (10) immune • diseases or modifications. The precise and predictable release kinetics afforded by the delivery systems as described in this invention render them particularly useful for the delivery of agents which have a narrow therapeutic window i.e., where the difference between the efficacious dose and toxic dose of the agent is low (ca. <5-fold) . Such agents include, in particular, those used to treat cardiovascular diseases, oncology diseases and endocrine diseases . Additional benefits may also be gained in the use of these systems for the delivery of agents requiring non- continuous or pulsatile release profiles to achieve therapeutic efficacy. Examples of classes therein include in particular macromolecules, such as hormonal proteins and peptides such as antiagents, antibodies, cytokines and growth promotants. Example of other bioactive agents include cancer cell inhibitory molecules, antimicrobials and antivirals derived from any native, synthetic or recombinant methods.

Suitable nutritional compounds, which are referred to in the art as "nutra-ceuticals" , include native and synthetic compounds such as vitamins, minerals, nutritional supplements and herbal agents. In the process the pharmaceutically active compound is dissolved in a solvent. The solvent is capable of penetrating the polyglycolide but is not capable of dissolving the polyglycolide.

In this specification, a solvent is considered capable of penetrating if it is capable of penetrating the polyglycolide to a degree of at least 1% measured as the mass increase when the polymer is immersed in the solvent, as a percentage of its initial mass. If it cannot penetrate to this degree it is considered incapable of penetrating.

In this specification a solvent is considered capable of dissolving the polyglycolide if it is capable of dissolving 0.2 grams polyglycolide in 100 ml solvent. The known systems involving HFIP are such that the solvent is capable of dissolving the polyglycolide and are excluded from the present invention. Preferably the solvent used in the invention is not capable of dissolving more than O.lg, more preferably not more than 0.05g, polyglycolide in 100 ml solvent . In the invention the solvent is liquid at atmospheric pressure and 20°C. The solvent may be an organic solvent . We have found that in some cases the solubility parameter S of the solvent can be used to predict whether it is likely to be suitable for use in the invention. The solubility parameter is, in the present invention, not the only indicator of suitability, and the essential characteristics are that the solvent should be capable of penetrating but not dissolving the polyglycolide. The solvent, whether organic or inorganic, can have any suitable solubility parameter provided the essential requirement is met, eg the solubility parameter can be from 18 to 50. However, we have found that within the class of organic solvents solubility parameters of from 18.5 to 28.0 Mpa¹², preferably 19.0 to 27.5 MPa¹², are especially suitable. Preferably the organic solvent is physiologically acceptable or pharmaceutically precedented. Thus the known solvents which dissolve polyglycolide, such as HFIP, are excluded from this preferred class of polymers.

Preferred solvents include dimethylsulphoxide, γ~ butyrolactone, N-methyl-2-pyrrolidone, dichloromethane, dimethyl malonate, propylene carbonate, acetone and chloroform, in particular dichloromethane and dimethyl malonate.

In the invention it is essential that the pharmaceutically active compound is dissolved in the solvent to form a solution of the pharmaceutically active compound.

In an alternative preferred embodiment the solvent is water, which is also incapable of dissolving polyglycolide but is capable of penetrating it.

The polymer may be formed into any suitable form or shape prior to impregnation, according to the intended form of the final implant to be produced. For instance, it may be in the form of films, sheets, membranes, rods, rings, tubes, porous structures, foams, meshes, moulded or extruded shaped objects (eg pins for bone or tissue fixation, screws or other designed shapes) , device components, staples, textiles, woven or knitted fabrics, feltworks, powders, beads, compressed tablets, monofilaments or braided sutures, and coatings.

Impregnation of the polyglycolide with the solution of pharmaceutically active compound is generally carried out at a temperature of from 15 to 50°C, preferably 20 to 45°C, more preferably 25 to 40°C. 50°C is the maximum preferred temperature since this minimises degradation of the pharmaceutically active compound. Contact of the solution with the polyglycolide is usually carried out for not more than 5 days, preferably not more than 3 days, and often not more than one day. In some cases impregnation may take less than 12 hours or less than 6 hours . After impregnation the polyglycolide is dried to remove substantially all the solvent. Preferably drying is carried out at a temperature of not more than 70°C, more preferably not more than 60°C, in particular not more than 50°C. Preferably drying is carried out for not more than 1 month, more preferably not more than two weeks, and in particular not more than one week.

Suitable impregnation times and drying times may be selected by the person skilled in the art. In particular, impregnation and drying may be monitored by weighing the sample.

To achieve the full benefit of the process of the invention, which does not require harsh processing conditions, the polymer is preferably not subjected to melting at any stage after initiation of contact with the solution of pharmaceutically active compound, and in particular is not subjected to any temperature above 100°C, preferably not subjected to any temperature above 70°C.

The onset and duration of release of the pharmaceutically active compound when the product is in use can be controlled by selection of the molecular weight of the polyglycolide and the implant size and geometry, as discussed below. The invention provides a convenient process for impregnating polyglycolide with drug and thus in a second aspect of the invention the product of the process of the first aspect of the invention is used as an implant. In this aspect we supply a pharmaceutically active compound to the body of a human or other animal subject by placing in the body of the subject an implant comprising an impregnated substantial homopolymer of glycolic acid produced by the process of the first aspect of the invention.

The implant may be applied to the body of the subject in any known manner, for instance surgical insertion, by mouth or powder injection.

An advantage of the invention is that it is possible to achieve pulsatile release. That is, the release profile is such that in the initial stages there is little if any release of pharmaceutical active and after a period of time a large amount of active is released over a short period. This type of release can advantageously be combined with an initial dose given by conventional means so that the product of the invention may be provided to give a "booster" dose of the same active or a different active. The invention also allows for the achievement of non- pulsatile release. In a third aspect of invention, we provide a product suitable for implantation in the body of a human or other animal subject comprising a pharmaceutically active compound encapsulated by a casing which forms a barrier between the pharmaceutically active compound and the environment, wherein at least part of the barrier is formed from a membrane of substantial homopolymer of glycolic acid.

Thus in this aspect of the invention we provide reservoir devices containing pharmaceutically active compound in which the casing or barrier of the reservoir device is at least in part formed from polyglycolide. Thus at least one part of the reservoir device is such that the only barrier between the pharmaceutically active compound and the environment is formed from a membrane of polyglycolide. We find surprisingly that devices of this type are capable of providing an entirely different release profile from those of the known reservoir devices. In particular, these devices can exhibit low or negligible drug release initially and a burst of pharmaceutically acceptable compound is released after a defined period of time. In this aspect of the invention the pharmaceutically active compound may be formulated in any suitable manner. Generally it is formulated with a pharmaceutically acceptable excipient . It may be in solid form (eg tablets, powders, granules) , semi-solid (eg creams, gels, ointments) or as a liquid, solution, suspension or emulsion.

The device may be in any suitable form, for instance a sealed tube formed from a polyglycolide membrane. It may be in the form of small capsules or packets. The entire casing may be formed from polyglycolide membrane. Alternatively at least part of the casing may be formed from other common non-biodegradable material, provided at least part of the barrier is polyglycolide only. For instance, a silicone O-ring sandwiched between two polyglycolide membranes may be used. The invention will now be illustrated with reference to the following examples. Examples Polymer and drugs

For all samples, polyglycolide (PGA) powder was purchased from Medisorb Technologies International, Ohio, lot number 97-12-143. Before processing, the molecular weight was 86,300. The manufacturer's data sheet gives the intrinsic viscosity as 1.3 dL/g, the glass transition temperature as 46.2°C and the melting point as 219°C. Samples contained theophylline, a bronchodilator used in the treatment of asthma. Theophylline was obtained in an anhydrous state from Sigma-Aldrich. Sample degradation

Degradation of all samples was carried out in phosphate-buffered saline solution (PBS) . The buffer solution was prepared from tablets purchased from Sigma- Aldrich, and contained 0.01 M phosphate buffer, 0.0027 M potassium chloride, and 0.137 M sodium chloride, with a. pH of 7.4. It was prepared with distilled water, and autoclaved at 120°C and 1 bar for 30 minutes before use. The buffer solution was filled into plastic bottles, which had first been autoclaved as described above, and the samples were suspended using cotton or nylon thread, or placed in Perspex sample holders. When samples were stirred during degradation this was done using a Variomag submersible magnetic stirrer. All samples were degraded in a water bath held at 37°C.

Measurement of basic sample properties Mass changes during solvent impregnation

Changes in sample mass during impregnation were measured accurately to 0.1 mg. The increase in mass due to the solvent was found as a percentage of the initial sample mass .

Ultra-violet spectrophotometry to measure drug release . The UN absorption of the buffer solution was measured daily using a Kontron UVIKOΝ 860 spectrometer with quartz cuvettes of path length 1 cm, and tested buffer solution was returned to the bottles after measurement to maintain the degradation volume. The drug concentration in the buffer solution was calculated, and cumulative drug release from the sample plotted. Example 1

In this example theophylline is incorporated into polyglycolide (PGA) with the use of an organic solvent. Sample preparation

PGA discs were manufactured on a Magnus compressible hot press, heated to 236 ± 2°C. Circular discs (diameter 15 mm) were pressed in an aluminium mould, of thickness 0.3 mm, which was placed between sheets of aluminium foil lubricated with PTFE spray to prevent the polymer from sticking to the press. An alternative method is to use a polyimide mould release film. The PGA was allowed to melt before pressing, to ensure that it filled the mould completely. The press was then closed, and the pressure was increased to 10 bar. The discs were pressed for 30 seconds, followed by immediate quenching in iced water. The samples obtained were amorphous and translucent, with a mass of approximately 80 mg. Samples prepared to any chosen size or geometry may be used, however.

The solvents used in the penetration tests may be compared with PGA in terms of solubility parameters. The solubility parameter of PGA was calculated using two different methods as approximately 24.4 (Coleman, .M. et al (1990) Polymer 31 1187-1203) or 25.0 (van Krevelen, D. W. (1990) Properties of Polymers 3rd Edition, Elsevier) MPa¹². Those of the solvents used are listed in Table 1 (Brandrup, J & Immergut, E.H. (1989) Polymer Handbook 3rd Edition, Wiley) . Table 1

Solvent Solubility parameter (MPa¹²)

Acetone 20.3

Dichloromethane 19.8

Dimethyl sulphoxide 24.6

Ethyl acetate 18.6

Methyl ethyl ketone 18.2

Toluene 19.0

The three solvents with the closest solubility parameters to PGA are able to penetrate the polymer, and the best penetration is given by DMSO, with the closest solubility parameter.

Figure 1 shows the release profile obtained when dimethyl malonate is used as the solvent. Impregnation was carried out with the sample suspended using cotton thread.

Degradation was carried out in 27 ml PBS with the sample suspended using nylon thread, with stirring.

Figure 2 shows the release profile obtained when dichloromethane is used as the solvent. Impregnation was carried out with the sample suspended in a copper wire basket. Degradation was carried out in 15ml PBS with the sample held in a perspex sample holder, without stirring. Each of these figures shows two sets of data, which are repeat experiments. Example 2

In this example the solvent used for incorporation of theophylline into PGA is water. We believe that the PGA is partially hydrolysed at the same time as impregnation occurs.

Experimental

In all cases, an 8 mg/ml aqueous theophylline solution was used. PGA discs prepared as in Example 1 and cut in half were suspended in approximately 20 ml of theophylline solution, using cotton thread. They were immersed for 2 days, and held at 37°C in a water bath, without stirring. The immersion time ensured that degradation was minimal, while the temperature was used to encourage ingress of water into the polymer. After impregnation, the samples were washed with distilled water to remove any drug left on the surface. Samples were dried under vacuum at room temperature for 3 days .

Figure 3 shows the drug release profile from one sample (dried before degradation) . Degradation was carried out in 15ml PBS with the sample suspended using cotton thread, without stirring. Example 3

In this example reservoir devices are demonstrated. The devices should be a way of giving a dose of a drug after a defined time period, determined by the thickness and molecular weight of the PGA film. This could be used to give a booster dose of a vaccine after a defined time period, of particular use in animal health applications. This removes the need for two treatments since both the initial dose and the reservoir device are applied at the same time. Experimental Reservoir membranes were produced on a hot press . A specific amount of polymer (measured by powder volume) was placed onto a certain surface area of PTFE-coated aluminium foil for pressing and films of chosen thickness made. A 20mm square of the polymer film was cut and folded in half, to form a pouch shape. A soldering iron at 230°C was used to seal the sides of the pouch. Contacting the soldering iron with the polymer caused rapid melting of the edges, and the molten polymer could then be smoothed down to effect a seal. The soldering iron did not appear to cause significant heating in the rest of the sample. The pouches were then filled with approximately 10 mg theophylline, and the soldering iron was used to seal the top of the pouch in the same way as the sides. Many other ways of producing the required reservoir topology may be used. These involve other geometries such as cylinders, and other methods of sealing. Drug release

Figure 4 shows the theophylline release profile from reservoir sample of thickness 0.18mm. The four data sets are repeat experiments . One sample shows a rapid change from very low to 100 % drug release, which can be attributed to the sample having prematurely broken apart .

The PGA membranes begin to erode after around 7 to 10 days, for the molecular weight studied. Substantial drug release begins when the membranes are fully porous and the time at which this occurs is related to the thickness of the membranes and the molecular weight of the polymer.

Several geometries and methods of sealing are possible, including heat sealing of an extruded tube, use of a circular resistance coil, with heat and pressure supplied to both sides of the seal, and laser welding.

Claims

1. A process for impregnating a substantial homopolymer of glycolic acid selected from substantial homopolymers of glycolic acid and block copolymers comprising at least 40 mol . % glycolic acid monomer as blocks which are substantial homopolymers of glycolic acid with a pharmaceutically active compound, the process comprising dissolving the pharmaceutically active compound in a solvent to form a solution of pharmaceutically active compound, contacting the solution with the polymer and allowing the solution to penetrate the polymer, characterised in that the solvent is liquid at atmospheric pressure and 20°C and is capable of penetrating the polymer and is not capable of dissolving the polymer.

2. A process according to claim 1 in which the solvent is an organic solvent .

3. A process according to claim 1 in which the solvent is water.

4. A process according to claim 2 in which the organic solvent has a solubility parameter S of from 18.5 to 28.0, preferably 19.0 to 27.5 MPa⁴⁴.

5. A process according to claim 2 in which the organic solvent is a physiologically acceptable solvent.

6. A process according to claim 2 in which the organic solvent is selected from the group consisting of dimethylsulphoxide, γ-butyrolactone , N-methyl-2- pyrrolidone, dichloromethane, dimethyl malonate, propylene carbonate, acetone and chloroform.

7. A process according to any preceding claim in which impregnation is carried out at a temperature of from 15 to 50°C, preferably 25 to 45°C, more preferably 30 to 40°C.

8. A process according to any preceding claim in which the solution is contacted with the polymer for a period of not more than 5 days, preferably not more than 3 days, and the solvent is subsequently removed by drying.

9. A process according to any preceding claim in which the polymer is a substantial homopolymer of glycolic acid.

10. A method of supplying a pharmaceutically active compound to the body of a human or other animal subject comprising placing in the body of the subject an implant comprising an impregnated polymer of glycolic acid produced by a process according to any preceding claim.

11. A method according to claim 10 in which the implant is supplied to the body by surgical insertion, by mouth or by powder injection.

12. Use of a product produced by the process of any of claims 1 to 9 in the manufacture of a medicament suitable for implantation in the body of a human or animal subject.

13. A product suitable for implantation in the body of a human or other animal subject comprising a pharmaceutically active compound encapsulated by a casing which forms a barrier between the pharmaceutically active compound and the environment, wherein at least part of the barrier is formed from a membrane of glycolic acid polymer selected from substantial homopolymers of glycolic acid and block copolymers comprising at least 40. mol . % glycolic acid monomer as blocks which are substantial homopolymers of glycolic acid.

14. A product according to claim 13 in which the pharmaceutically active compound, optionally with pharmaceutically acceptable excipient, is in the form of a semi-solid, liquid, solution, suspension or emulsion.

15. A product according to claim 13 in which the pharmaceutically active compound, optionally with pharmaceutically acceptable excipient, is in the form of a solid.

16. A product suitable for implantation in the body of a human or other animal subject comprising an impregnated polymer of glycolic acid obtainable by the process of any of claims 1 to 9.