WO2012122643A1 - Injection assist device and method - Google Patents

Abstract

An injection assist device for automatically injecting a medicament into a subject once the device has been triggered. The device includes a medicament chamber and a plunger for injecting medicament from the medicament chamber through a needle, a retaining mechanism for securing the plunger against movement in a distal direction when the device is in an armed configuration, and an activator that slidingly and rotationally displaces the retaining mechanism when the device is triggered to allow distal movement of the plunger to inject the medicament from the medicament chamber through the needle. Methods of administering an injection using the device are provided.

Description

INJECTION ASSIST DEVICE AND METHOD

Reference to Related Applications

[0001] For purposes of the United States of America, this application claims the benefit of U.S. provisional patent application No. 61/451,974 filed 11 March 2011, which is hereby incorporated by reference herein in its entirety for all purposes.

Technical Field

[0002] Embodiments of the present invention relate to devices and methods for delivering medicament to a subject, and in particular to devices and methods for automatically injecting medicament once an injection device has been triggered.

Background

[0003] Auto-injection devices for injecting medicament automatically (i.e. without a user physically inserting a needle into a subject and/or compressing a plunger to administer the medicament) are known. Examples of such devices presently in use are the EpiPen™ and Twinject™. Such devices may be used, for example, to prevent or ameliorate the effects of anaphylaxis caused by allergic reaction, for example caused by contact with certain foods, medications, insect venom or latex. The allergic reaction causes the body to release histamine and other substances which causes blood vessels to dilate (lowering blood pressure) and fluid to leak into the tissues (causing swelling). Anaphylaxis can cause constriction of the airways, wheezing, difficulty breathing, stomach cramps, vomiting and diarrhea. This condition varies in its severity from person to person. More severe cases can lead to anaphylactic shock, and possibly death.

[0004] Anaphylaxis can be countered by using various drugs. One drug commonly used to treat or prevent anaphylaxis is epinephrine (adrenaline). Epinephrine increases the heart rate, counteracts the effects of histamine, and stabilizes the membranes of the cells that release histamine, preventing further histamine release, which in turn counteracts the effects of anaphylaxis. Early treatment is important to survival of anaphylaxis. Initial first aid in the form of self- administration of epinephrine, such as by an autoinjection device, at the first sign of anaphylaxis is recommended. [0005] Auto-injection devices also have applicability in other fields, for example the rapid administration of antidotes to counteract the effects of chemical or biological weapons; the administration of morphine, ketamine, and other pain management drugs on the battlefield or in emergency situations; administration of glucagon for diabetics; administration of antidotes to counteract the effects of venoms and poisons;

administration of veterinary agents; or the like. [0006] Auto-injection devices should be of relatively small size to allow users to readily carry the auto-injection device with them at all times. There is a need for smaller auto-injection devices than those presently available. In some cases, it is desirable to have an auto-injection device of a smaller overall size. In some cases, it is desirable to have an auto-injection device having a relatively longer needle, for example for use by a person with a relatively higher body fat level, while still not increasing the overall size (i.e. exterior dimensions) of the device. Brief Description of Drawings

[0007] Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

[0008] Figure 1 is a front view of an embodiment of an injection assist device in the assembled state.

[0009] Figure 2 is a cross-sectional view of the embodiment of Figure 1 in the assembled state.

[0010] Figure 3 is an exploded longitudinal view of the embodiment of Figure 1.

[0011] Figure 4 is an exploded longitudinal sectional view of the embodiment of Figure 1.

[0012] Figure 5 is a longitudinal sectional view of a housing of an injection assist device according to one embodiment.

[0013] Figure 6 is a perspective view of the activator of one embodiment of the invention.

[0014] Figure 7 is a partial cross-sectional view showing the engagement between the activator and the retaining prong on the housing in the embodiment of Figure 1.

[0015] Figures 8A and 8B are partial cut-away views of the embodiment of Figure 1 showing the engagement of the activator, the plunger prongs, and the retaining extension, with the activator in the triggering position.

[0016] Figure 9 A is a partial cut-away view that shows the configuration of one of the plunger prongs, the activator and the corresponding retaining prong just at the point when the embodiment of Figure 1 is triggered. Figure 9B is a partial cut-away view that shows the configuration of one of the plunger prongs, the activator and the corresponding retaining prong just after the injection assist device has been triggered, as the plunger moves distally relative to the housing.

[0017] Figure 10A is a cross-sectional view that shows the engagement between the plunger prongs and the retaining extensions of the housing in the embodiment of Figure 1 when the device is in the armed configuration. Figure 10B is a cross-sectional view that shows the position of the plunger prongs within the plunger channels of the housing when the device is in the triggered configuration.

[0018] Figure 11 is a partial longitudinal sectional view of a further embodiment of an injection assist device.

[0019] Figure 12 is an exploded longitudinal sectional view of the embodiment of Figure 11.

[0020] Figure 13 is a longitudinal sectional view of the housing of the embodiment of Figure 11.

[0021] Figure 14 is a perspective view of the activator of the embodiment of Figure 11.

[0022] Figure 15 is a perspective view of the plunger of the embodiment of Figure 11.

Description

[0023] Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

[0024] As used herein, the term "distal" means a direction along the length of the injection assist device towards an injection site where medicament is to be

administered, and the term "proximal" means a direction along the length of the injection assist device away from the injection site. "Radially inward" means a direction towards an axial centerline of the injection assist device. "Radially outward" means a direction away from an axial centerline of the injection assist device.

"Axially" means a direction along an axial centerline of the injection assist device.

[0025] As used herein, the term "medicament" includes any substance to be injected into a subject. The medicament is typically, but is not limited to, a drug intended for intramuscular injection.

[0026] With reference to Figures 1-4, in one embodiment an injection assist device 20 has a housing 22 with an activator 24 slidably disposed therein. Housing 22 has a needle 26 at its distal end for injecting medicament 28 into a patient. A medicament chamber 30 is in fluid communication with needle 26 and contains medicament 28. A plunger 32 is sealingly engaged within medicament chamber 30 to inject medicament 28 through needle 26 upon application of an injection force. Plunger 32 is initially secured in place by a release mechanism 34. When a user applies a triggering force, for example by pressing the distal end of activator 24 firmly against the skin of the subject to whom medicament 28 is to be administered, activator 24 slides in the proximal direction, thereby contacting release mechanism 34 and causing release mechanism 34 to be slidingly and rotationally displaced. The release of release mechanism 34 following its sliding and rotational displacement allows the force applied by an actuator 36 to displace plunger 32 in the distal direction, thereby injecting medicament 28 into the subject.

[0027] An advantage of some embodiments of the present invention is that the sliding and rotational displacement permitted by release mechanism 34 allows the manufacture of an injection assist device having a shorter length than may be achieved using other release mechanisms. Such embodiments may provide the same dosage of medicament while having an overall smaller size, and thus greater portability, as compared to known auto-injectors. Some embodiments of the present invention also allow for the use of a needle of relatively larger size without increasing the overall size of the device.

[0028] As shown in Figure 5, in the illustrated exemplary embodiment housing 22 is generally cylindrically shaped. A first set of threads 38 is provided at or near the proximal end of housing 22 for securing an end cap 40 in place. A second set of threads 42 is provided at or near the distal end of housing 22 for securing a needle end cap 44. A clip, clasp, or other suitable securing means (not shown) can optionally or alternatively be provided to secure needle end cap 42 to housing 22. In the illustrated embodiment of Figures 1-10, the interior surface of housing 22 includes three activator channels 46 for slidably receiving activation prongs 56 of activator 24, and three plunger channels 48 for slidably receiving plunger prongs 70 of plunger 32, as described below. Housing 22 also includes a receptacle 50 at its distal end that accommodates sliding movement of activator 24 between its initial resting state and its triggering state, as described below. In the illustrated embodiment, the distal portion of housing 22 also includes a medicament chamber support 49, which can help to prevent movement of medicament chamber 30 in the distal direction, and which includes an aperture therein through which needle 26 can pass.

[0029] A medicament chamber 30 (Figures 2 and 3) is secured within housing 22 to hold medicament 28. Medicament chamber 30 may be secured within housing 22 in any suitable manner, such as by friction fit or suitable adhesives. In some

embodiments, medicament chamber 30 is generally cylindrical in shape. Medicament chamber 30 accommodates plunger 32 in a slidable, sealing engagement therein, so that plunger 32 will force medicament out of medicament chamber 30 when an injection force is applied. Plunger 32 may have a seal 64 at its distal end made of rubber or soft plastic for the purpose of providing a sliding, sealing engagement with medicament chamber 30. [0030] Medicament chamber 30 and plunger 32 are sized to deliver the desired dose of medicament 28. In some embodiments, the components of injection assist device 20 are sized to deliver up to an 0.6 mL dose of liquid medicament, such as epinephrine. In some embodiments, the dosage of medicament 28 can be set for a volume between 0.1 mL and 0.6 mL, including any value therebetween, e.g. 0.15 mL, 0.20 mL, 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, 0.50 mL, or 0.55 mL. In some embodiments, a dosage volume of 0.6 mL may correspond to a dosage of 0.6 mg of liquid medicament. In some embodiments, the dosage of medicament is in the range of 0.1 mg to 0.6 mg or any value therebetween, e.g. 0.15 mg, 0.20 mg, 0.25 mg, 0.30 mg, 0.35 mg, 0.40 mg, 0.45 mg, 0.50 mg, or 0.55 mg. The dosage may be varied by setting plunger 32 a predetermined distance distally of medicament chamber 30 during manufacture, by diluting medicament 28, or in any other manner suitable to vary the volume or concentration of medicament 28 administered by injection assist device 20.

[0031] Injection assist device 20 can be configured to deliver any desired dosage of medicament. In some embodiments, the dosage of medicament 28 provided by injection assist device 20 is modified by diluting the concentration of the drug contained within medicament chamber 30. For example, in some embodiments, the components of injection assist device 20 are sized to inject an 0.6 mL volume of medicament. The amount of drug injected is varied by varying the concentration of the drug in medicament chamber 30. For example, in embodiments where injection assist device 20 is used to administer epinephrine, for a device intended for use by large adults, the concentration of epinephrine within medicament chamber 30 may be about 1 mg/mL, such that injection assist device 20 is configured to provide an 0.6 mg dose of epinephrine. A device intended for use by smaller adults may have a concentration of epinephrine within medicament chamber 30 of about 0.67 mg/mL, such that injection assist device 20 is configured to provide an 0.4 mg dose of epinephrine. A device intended for use by children may have a concentration of epinephrine within medicament chamber 30 of about 0.33 mg/mL, such that injection assist device 20 is configured to provide an 0.2 mg dose of epinephrine. The concentration of drug within medicament chamber 30 could readily be modified by one skilled in the art to achieve any desired dosage amount. [0032] In some embodiments where it is desired to regulate the amount of medicament injected by injection assist device 20, plunger 32 may be provided with a radially outwardly projecting rim or lip 33 (Figure 4). Lip 33 may engage with a radially inwardly projecting stop (not shown) or other suitable structure on the inside surface of housing 22 or on medicament chamber 30, to stop movement of plunger 32 in the distal direction before substantially all of medicament 28 has been injected. The amount of medicament 28 that will be injected can be regulated by varying the distance between lip 33 and the stop or other suitable structure during manufacture of plunger 32. For example, in embodiments where it is desired to administer a smaller volume of medicament 28, lip 33 is placed relatively closer to the distal end of plunger 32, so that distal motion of plunger 32 will be stopped before all of the medicament 28 has been injected. Alternatively, in some embodiments where it is desired to administer a smaller volume of medicament 28, plunger 32 is made of a relatively longer length, so that the initial resting position of seal 64 is relatively more distally located within medicament chamber 30, which will result in the injection of a smaller volume of medicament 28 when device 20 is triggered.

[0033] Medicament chamber 30 is retained within housing 22 in fluid communication with needle 26. Needle 26 is affixed to medicament chamber 30 or housing 22 in any suitable manner, for example by cementing, crimping, or with any suitable adhesive. In the illustrated embodiment, needle 26 is affixed to a needle stabilizer 52, which is affixed to the distal end of medicament chamber 30. Needle 26 may be affixed to medicament chamber 30 or housing 22 in any suitable manner, for example by cementing, crimping, or using any suitable adhesive to secure needle 26 to needle stabilizer 52.

[0034] In embodiments where injection assist device 20 is to be used as an emergency auto-injector, the size and length of needle 26 should be selected to ensure that needle 26 will deliver medicament 28 into the muscle of a subject, and so that needle 26 will be sufficiently strong to penetrate e.g. both clothing and skin without deflecting during insertion into the subject. The range of needle gauges that may be used with device 20 may be up to the same size as the inner diameter of activator 24, although preferably the needle gauge is less than the diameter of re-extension spring 96. In some embodiments intended for use by humans, needle 26 is anywhere between a 14 gauge needle and a 26 gauge needle, or any value therebetween, e.g. 15 gauge, 16 gauge, 17 gauge, 18 gauge, 19 gauge, 20 gauge, 21 gauge, 22 gauge, 23 gauge, 24 gauge, or 25 gauge. In some embodiments, needle 26 is a 21 gauge needle. [0035] Needle 26 may be of any suitable length. In some embodiments, needle 26 has a length of 1/2 inch to 2 inches, or any value therebetween, e.g. 3/4 inch, 7/8 inch, 1 inch, 1 and 1/8 inch, 1 and 1/4 inch, 1 and 3/8 inch, 1 and 1/2 inch, 1 and 5/8 inch, 1 and 3/4 inch, or 1 and 7/8 inch. In some embodiments, needle 26 has a length of 1/2 inch. In some embodiments, needle 26 has a length of 1 inch. In some embodiments, needle 26 has a length of 3/4 inch. In some embodiments where needle 26 has a length of up to 1 inch, the overall dimensions of device 20 are the same as embodiments in which needle 26 has a length of 1/2 inch. [0036] The size and length of needle should be selected based on the intended user for the device. For example, in embodiments intended for use by an average-sized adult, needle 26 may have a length of 1 inch. In embodiments intended for use by a larger- sized adult or an obese person, needle 26 may have a length of 1 inch, and possibly longer in some embodiments. In embodiments intended for use by a child, needle 26 may have a length of 3/4 inch. Embodiments having a relatively larger needle size may also be configured to deliver a relatively larger dose of drug from medicament chamber 30, for example by having a higher concentration of medicament therein.

[0037] In some embodiments, injection assist device 20 has a needle 26 that is a 21 gauge needle one inch in length, and device 20 is configured to provide an 0.6 mg dose of epinephrine. In some embodiments, injection assist device 20 has a needle 26 that is a 21 gauge needle one inch in length, and device 20 is configured to provide an 0.4 mg dose of epinephrine. In some embodiments, injection assist device 20 has a needle 26 that is a 21 gauge needle 3/4 inch in length, and device 20 is configured to provide an 0.2 mg dose of epinephrine.

[0038] In the illustrated embodiment, needle 26 is generally shielded by main body 54 of activator 24 prior to use. Activator 24 is slidably disposed within housing 22 so that it is slidable between a resting position generally shielding needle 26 and a triggering position contacting release mechanism 34, with needle 26 exposed, as described below. As best shown in Figure 6, activator 24 includes a generally cylindrical main body 54 at its distal end, and axially extending activation prongs 56 at its proximal end.

Activation prongs 56 are slidably disposed within activator channels 46 of housing 22. Angled activation surfaces 58 are provided at the proximal end of activation prongs 56. Main body 54 is slidably disposed within receptacle 50 of housing 22. Activator 24 is thus slidable in an axial direction with respect to housing 22. [0039] Receptacle 50 of housing 22 is generally cylindrical in shape to accommodate main body 54. In the illustrated embodiment, receptacle 50 has a slightly larger diameter than the rest of the interior surface of housing 22, so that a lip 51 (Figures 2 and 3) is formed at the proximal end of receptacle 50. Once activator 24 has triggered release mechanism 34 as described below, further proximal motion of activator 24 will cause lip 51 to contact the proximal edge of main body 54, preventing further movement of activator 24 in the proximal direction.

[0040] Retaining features may be provided on the exterior surface of activator 24 and on housing 22 to prevent ejection of activator 24 from housing 22. As best shown in Figure 7, in the illustrated embodiment housing 22 is provided with three

circumferentially spaced retaining hooks 41. Retaining hooks 41 project radially outwardly from an internal portion of the distal end of housing 22. Retaining hooks 41 are slidably engaged within channels 43 on the interior surface of main body 54 of activator 24. A retaining surface 45 is formed at the proximal end of each channel 43. Retaining hooks 41 engage with retaining surfaces 45 to prevent activator 24 from sliding completely out of housing 22 in the distal direction. Retaining hooks 41 and retaining surfaces 45 together provide a retaining feature. [0041] In the illustrated embodiment, retaining hooks 41 are somewhat flexible.

During assembly, activator 24 can be slid proximally over retaining hooks 41 and into housing 22. Retaining hooks 41 initially flex radially inwardly to allow activator 24 to be slid over the retaining hooks. Once a retaining surface 45 on activator 24 is slid past a corresponding retaining hook 41 , retaining hook 41 enters its corresponding channel 43 and flexes radially outwardly back to its resting position therein.

[0042] Securing features can optionally be provided to secure activator 24 in its initial resting position. In the illustrated embodiment of Figures 1-10, a pair of radially outwardly extending circumferential protrusions 57 on an outside surface of main body 54 of activator 24 gently engage with a radially inwardly extending circumferential protrusion 59 provided on the inside surface of housing 22. The engagement of protrusions 57 with protrusion 59 maintains activator 24 in its resting position during day-to-day activities of the person carrying device 20. The engagement is easily overcome by a user when device 20 is triggered.

[0043] With reference to Figures 8 A and 8B, activation prongs 56 include sloped activation surfaces 58 at their distal ends. Activation surfaces 58 engage with correspondingly sloped activation surfaces 60 on activation prongs 72 of plunger 32, as described below. Activation surfaces 58 are angled in a direction to cause plunger 32 to rotate in a direction towards plunger channels 48 within housing 22 when device 20 is triggered. [0044] The angle Θ formed by sloped activation surfaces 58 relative to a notional radial cross-section of housing 22 should be approximately complementary to the angle φ relative to the axial direction formed by sloped activation surfaces 60 at the distal end of activation prongs 72 of plunger 32, described below. The use of approximately complementary angles facilitates the smooth sliding of surfaces 60 relative to surfaces 58 when injection assist device 20 is triggered. Injection assist device 20 is "triggered" when release mechanism 34 is rotationally and axially displaced from its initially secured armed position to a triggered position that allows movement of plunger 32 in the distal direction. In typical embodiments, angles Θ and φ vary between about 15° to about 75°, and may be any angle therebetween, including e.g. about 18°, 20°, 22°, 24°, 26°, 28°, 30°, 32°, 34°, 36°, 38°, 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 49°, 50°, 52°, 54°, 56°, 58°, 60°, 62°, 64°, 66°, 68°, 70°, or 72°. In some embodiments, angle Θ is between about 30° and about 60°. In some embodiments, angle φ is between about 30° and about 60°. In some embodiments, angle Θ is 45°. In some embodiments, angle φ is 45°. In some embodiments, angles Θ and φ are each 45°.

[0045] While in the illustrated embodiment activation surfaces 58 and 60 are shown as smoothly angled surfaces (e.g. as best shown in Figures 8A and 8B), it will be appreciated that variations in shape that do not interfere with the relative sliding motion of surfaces 58 and 60, and with the relative sliding motion of surfaces 60 and triggering surfaces 80 as described below, can also be used. For example, small indentations on surfaces 58 and 60, gently curved surfaces, any type of projection and complimentary groove that can mate together for the purpose of providing sliding and rotational displacement of plunger 32 when device 20 is triggered, or any other surface features that do not interfere with the relative sliding motion of surfaces 58 and 60 are possible.

[0046] Plunger 32 includes a seal 64 at its distal end for sealingly but slidingly engaging with the interior surface of medicament chamber 30. Seal 64 may be made from a material such as rubber or soft plastic. Plunger 32 includes a spring retainer, which in the illustrated embodiment is a cylindrical extension 66 at the distal end of plunger 32 that is sized and configured to contain power spring 68, as described below. Plunger 32 is selectively movable both in the axial direction parallel to axis 69 of housing 22 and rotationally about axis 69. In the illustrated embodiment, plunger 32 is selectively retained by release mechanism 34. Plunger 32 is axially slidable within plunger channels 48 of housing 22 when plunger 32 is released by release mechanism 34.

[0047] In the illustrated embodiment of Figures 1-10, release mechanism 34 is provided by three plunger prongs 70. Plunger prongs 70 extend radially outwardly from the main body of plunger 32. Each illustrated plunger prong 70 includes a generally triangularly shaped activation prong 72 and a generally triangularly shaped retaining prong 74 (Figures 8A and 8B). Prongs 72 and 74 project in the distal direction from plunger prongs 70. Each activation prong 72 includes an angled activation surface 60 on the distal end thereof, and a generally axially extending securing surface 76 adjacent thereto.

[0048] Each securing surface 76 engages with a retaining extension 78 of housing 22. In the illustrated embodiment as best shown in Figure 5, retaining extensions 78 project radially inwardly from housing 22. Each retaining extension 78 is defined on the inside surface of housing 22 between one activator channel 46 and the adjacent plunger channel 48. Retaining extension 78 has an angled triggering surface 80 at its proximal end. The shape of angled triggering surface 80 is preferably approximately

complementary to that of activation surface 60, to permit activation surfaces 60 to easily slide past triggering surfaces 80 when injection assist device 20 is triggered. In some embodiments, the angle ψ of angled triggering surfaces 80 relative to a notional radial cross section of housing 22 is approximately complementary to the angle φ of activation surfaces 60. In typical embodiments, the angle ψ of angled triggering surfaces 80 is between about 15° to about 75°, and may be any angle therebetween, including e.g. about 18°, 20°, 22°, 24°, 26°, 28°, 30°, 32°, 34°, 36°, 38°, 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 49°, 50°, 52°, 54°, 56°, 58°, 60°, 62°, 64°, 66°, 68°, 70°, or 72°. In some embodiments, angle ψ is between about 30° to about 60°. In some embodiments, the angle ψ of angled triggering surfaces 80 is 45°. In some

embodiments, angle ψ is the same as angle Θ.

[0049] As with activation surfaces 58 and 60, variations in shape of triggering surface 80 that do not interfere with the relative sliding motion of surfaces 60 and 80 can also be used. For example, small indentations on triggering surface 80, a gently curved surface, or any other surface features that do not interfere with the relative sliding motion of surfaces 60 and 80, are possible.

[0050] Prior to use, when injection assist device 20 is in the armed configuration, each activation prong 72 sits within a corresponding activator channel 46. Power spring 68 applies force against plunger 32 in the distal direction to hold activation prong 72 within activator channel 46. Retaining extension 78 engages with securing surface 76 to prevent rotational movement of plunger 32 until injection assist device 20 is activated.

[0051] While securing surface 76 is illustrated as a generally smooth surface, it will be appreciated that minor variations in the shaping of surface 76 that do not interfere with the engagement between securing surface 76 and retaining extension 78 to prevent rotational movement of plunger 32, or with the distal sliding of securing surface 76 relative to retaining extension 78 during activation, may be used.

[0052] Plunger prongs 70 include a retaining feature to prevent distal displacement of plunger 32 when injection assist device 20 is in the armed configuration. In the illustrated embodiment, retaining prongs 74 extend radially outwardly from plunger 32 and are located adjacent activator prongs 72. Retaining prongs 74 provide the retaining feature. In some embodiments, retaining prong 74 includes an angled surface 82 at its distal end. In the illustrated embodiment, the angle formed by the slope of angled surface 82 at the distal end of retaining prong 74 is complementary to that of triggering surface 80. Together angled surface 82 and securing surface 76 define a groove 84. In the illustrated embodiment, groove 84 is complementary in shape to the proximal end of retaining extension 78. In some embodiments, the angle formed by angled surface 82 relative to the axial direction is the same as angle φ. In typical embodiments, the angle formed by angled surface 82 is between about 15° to about 75°, and may be any angle therebetween, including e.g. about 18°, 20°, 22°, 24°, 26°, 28°, 30°, 32°, 34°, 36°, 38°, 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 49°, 50°, 52°, 54°, 56°, 58°, 60°, 62°, 64°, 66°, 68°, 70°, or 72°. In some embodiments, the angle formed by angled surface 82 may be between about 30° and about 60°. In some embodiments, the angle formed by angled surface 82 may be 45°. [0053] The shape of retaining prong 74 may be varied and the shape of retaining extension 78 may be varied, so long as such variations do not interfere with the distal sliding of plunger 32 relative to retaining extension 78 when injection assist device 20 is triggered, or with the rotational movement of plunger 32 relative to housing 22 when injection assist device 20 is triggered.

[0054] In the armed position, activation prong 72 is received within activation channel 46. Securing surface 76 and retaining prong 74 engage with retaining extension 78. Retaining extension 78 is securely received within groove 84 in the illustrated embodiment. The distal force applied by power spring 68 securely pushes each plunger prong 70 (and thus each groove 84, if present) against the corresponding retaining extension 78. Retaining extensions 78 in combination with plunger prongs 70 thus prevent distal and rotational displacement of plunger 32 until injection assist device 20 is triggered.

[0055] In the illustrated embodiment of Figures 1-10, three activation prongs 56, three activator channels 46, three release mechanisms 34, and three plunger channels 48 are provided. However, the number could be varied. For example, two activation prongs, two activator channels, two release mechanisms, and two plunger channels could be used in some embodiments. Alternatively, four activation prongs, four activator channels, four release mechanisms, and four plunger channels could be used in some embodiments. The activation prongs and release mechanisms are preferably distributed generally symmetrically around the circumference of housing 22.

[0056] In the illustrated embodiment, power spring 68 is a compressed coil spring. However, any suitable actuation system, such as e.g. a pneumatic actuator, could alternatively be used in place of a compressed coil spring. Power spring 68 is secured between end cap 40 and the body of plunger 32, and is compressed when injection assist device 20 is in the armed state. Extension of power spring 68 when device 20 is triggered provides the injection force to move plunger 32 in the distal direction and cause injection of medicament 28. Cylindrical extension 66 contains and supports power spring 68 to help prevent spring 68 from buckling during compression. [0057] Any suitable spring may be used as power spring 68. In one exemplary embodiment, power spring 68 has a diameter of 4 mm, the wire diameter of power spring 68 is 1 mm, and power spring 68 has a spring constant of approximately 5.34 N/mm. [0058] End cap 40 may be secured to housing 22 in any suitable manner, such as by threaded engagement, suitable adhesives, or the like. In the illustrated embodiment, end cap 40 includes a threaded surface 86 for engagement with corresponding threads 38 of housing 22. Threaded surface 86 is provided on the outside surface of end cap 40 while threads 38 are provided on the inside surface of housing 22. It will be appreciated that the relative orientation of threads 38 and 86 could be reversed. End cap 40 may alternatively or additionally be secured in place using a suitable adhesive such as, for example, an epoxy adhesive. The engagement between end cap 40 and housing 22 may be sufficiently close to ensure that contaminants cannot enter housing 22. In some embodiments, the engagement between end cap 40 and housing 22 is waterproof. In some embodiments, end cap 40 is not provided but rather housing 22 is shaped so as to have a closed proximal end. [0059] End cap 40 or housing 22 optionally includes a portability feature, such as carrying handle 88 in the illustrated embodiment. In some embodiments, carrying handle 88 may be attached to a keychain, lanyard or the like, to facilitate the transport of injection assist device 20 by a potential user. [0060] Needle end cap 44 is provided to be secured over the distal end of housing 22, and over needle 26, when injection assist device 20 is not in use. Needle end cap 44 may be removably secured to housing 22 in any suitable manner such as by friction fit, snap-fit, or threaded engagement. In some embodiments, suitable clips or clasps (not shown) are provided to alternatively or additionally secure needle end cap 44 to housing 22. In the illustrated embodiment, needle end cap 44 includes threads 90 on the proximal inner surface thereof. Threads 90 are engageable with correspondingly threaded surface 42 of housing 22. In some embodiments, threaded surfaces 42 and 90 are configured so that needle end cap 44 can be unscrewed in just under one rotation. [0061] One or more suitable seals may be provided to ensure that the interior of injection assist device 20 remains sterile prior to use. For example, a thin rubber seal 94 may be provided within the main body 54 of activator 24, to provide a moisture barrier to keep moisture from entering the interior of housing 22. In the illustrated embodiment, an O-ring type seal 92 is also provided between housing 22 and activator 24 to provide a seal between the interior of housing 22 and the external environment. In some embodiments, seal 92 renders injection assist device 22 waterproof, i.e.

permits exposure of device 22 to a significant level of humidity or even submersion in water without adversely affecting the performance or reliability of device 22. [0062] In some embodiments, e.g. as best shown in Figure 7, a re-extension spring 96 is provided, to exert a distal force on activator 24. Re-extension spring 96 is sufficiently weak to avoid interference with the activation of injection assist device 20. However, re-extension spring 96 applies a distal force against activator 24 to hold it at its most distal (i.e. resting) position with respect to housing 22, thereby covering needle 26 when device 20 is not being used to inject a subject. In the illustrated embodiment, re-extension spring 96 is positioned to be compressed between activator 24 and housing 22 when activator 24 is pressed against a subject. Re-extension spring 96 applies an extension force to slide activator 24 back to its original position covering needle 26 once injection assist device 20 is moved away from the subject.

[0063] Suitable materials for construction of injection assist device 20 can be selected by those skilled in the art. For example, housing 22 and activator 24 may be made from a plastic material such as, for example, ethylene vinyl acetate with a ratio of 12% vinyl acetate. Housing 22 may be made from a material that is opaque to impede the passage of ultraviolet light, since ultraviolet light may reduce the effective shelf life of the medicament 28 contained within medicament chamber 30. Plunger 32 may be made from a material such as nylon (e.g. Type 66, 60% long glass fiber). Medicament chamber 30 may be made from a material that will be compatible with medicament 28, for example, ceramic glass.

[0064] To use injection assist device 20, needle end cap 44 is unscrewed by a user. In some embodiments, needle end cap 44 is designed so that it can be unscrewed by a user in just under one rotation to facilitate removal by a user. Injection assist device 20 is positioned approximately perpendicularly against the skin of a subject to whom medicament 28 is to be administered. The distal end of injection assist device 20 is placed on the skin of the subject at the desired injection site. For administration of an intramuscular injection, the desired injection site will generally be a region of the body with a large muscle mass, such as the thigh of a subject.

[0065] The user then presses firmly in the distal direction on housing 22. The distal end of activator 24 is held against the skin of the subject, causing activator 24 to slide proximally relative to housing 22. Proximal movement of activator 24 exposes needle 26. Continued distal movement of housing 22 towards the subject causes needle 26 to be inserted into the subject, in preparation for administration of medicament 28. Main body 54 of activator 24 may largely shield needle 26 from view throughout the injection process.

[0066] Relative motion of activator 24 and housing 22 causes activation prongs 56 to slide proximally within activator channels 46. When activator 24 moves to the triggering position, activation surfaces 58 of activation prongs 56 make contact with activation surfaces 60 of plunger prongs 70. Continued proximal movement of activator 24 relative to housing 22 causes angled activation surfaces 58 to apply both axial force in the proximal direction and rotational force against plunger prongs 70. [0067] When injection assist device 20 is in the armed configuration, plunger prongs 70, and thus plunger 32, are prevented from rotating relative to housing 22 by engagement of securing surfaces 76 with retaining extension 78. When device 20 is triggered, plunger 32 is displaced axially in the proximal direction relative to housing 22, thereby causing securing surfaces 76 to move axially past retaining extensions 78 in the proximal direction.

[0068] Figures 9A and 10A show the configuration of one of the activation prongs 56, the corresponding retaining extension 78 on housing 22, and plunger prong 72 when injection assist device 20 is triggered. Plunger prongs 70 are initially resting on retaining extensions 78 with activation prongs 72 within activator channels 46. Once securing surfaces 76 have moved axially in the proximal direction past retaining extensions 78, rotational movement of plunger 32 relative to housing 22 is possible. The continued force applied by angled activation surfaces 58 of activator 24 causes plunger 32 to rotate within housing 22 in a direction away from activation prongs 56 of activator 24 and toward plunger channels 48. The distal force applied by power spring 68 causes activation surfaces 60 of plunger prongs 70 to slide past angled activation surfaces 58 of activator 24, and past angled triggering surfaces 80 of retaining extensions 78.

[0069] Figures 9B and 10B show the configuration of the activation prongs 56, the retaining extensions 78 on housing 22, and the plunger prongs 72 after injection assist device 20 has been triggered. Continued rotational and distal movement of plunger 32 relative to housing 22 causes plunger prongs 70 to move into plunger channels 48. Plunger 32 has thus moved from its initial armed position to a triggered position, allowing plunger 32 to operate to inject medicament 28. Plunger 32 slides axially in the distal direction relative to housing 22 within plunger channels 48 under the force applied by power spring 68, thereby administering medicament 28 through needle 26. In some embodiments, plunger channels 48 are dimensioned to prevent any further rotational movement of plunger 32 after plunger 32 enters plunger channels 48, for example by being sized to just accommodate sliding axial movement of plunger prongs 70. The exact shape and configuration of plunger channels 48 is not critical, so long as plunger 32 can slide axially in the distal direction to inject medicament 28. [0070] Distal movement of plunger 32 will stop when plunger 32 has reached the distal portion of medicament chamber 30, by which point substantially all of medicament 30 will have been injected into the subject. Alternatively, movement of plunger 32 may be stopped by engagement of lip 33 of plunger 32 with a suitable stop provided on the interior of housing 22 or on medicament chamber 30, as described above.

[0071] Following injection of medicament 28, a user withdraws needle 26 from the subject. In some embodiments, the user may wait a predetermined period of time after triggering injection assist device 20 prior to withdrawing needle 26, to ensure that all medicament 28 has been injected. The force applied by optional re-extension spring 96 pushes activator 36 distally relative to housing 22, so that main body 54 of activator 24 covers needle 26. The user can then screw needle end cap 44 back onto threaded surface 42 of housing 22 to ensure needle 26 is covered.

[0072] If further medical care is required, injection assist device 20 can accompany the subject in its capped and discharged state so that the person providing further care to the subject can readily see the type and dosage of medicament 28 that has been administered to the subject.

[0073] With reference to Figures 11-15, a further embodiment of an injection assist device 120 is illustrated. Components of injection assist device 120 that perform the same function as components of injection assist device 20 are labeled with like reference numerals incremented by 100, including housing 122, actuator 124, needle end cap 144, plunger 132, power spring 168, and proximal end cap 140. Injection assist device 120 functions in generally a similar manner to injection assist device 20. Injection assist device 120 has been modified to receive a conventional or standard syringe assembly 102. As used herein, the term "conventional syringe assembly" or "standard syringe assembly" means a commercially available syringe barrel, e.g. as manufactured for use with a standard plunger, barrel and needle. An example of a commercially available syringe that can be used to provide a standard syringe assembly in embodiments of the present invention is the HYPAK™ syringe manufactured by Becton, Dickinson and Company.

[0074] Standard syringe assembly 102 includes a needle 126 at its distal end, a narrow distal portion 104, a main cylindrical body 106, and a proximal securing element 108. Needle 126 is in fluid communication with a medicament chamber 130 formed within main cylindrical body 106. In the illustrated embodiment, proximal securing element 108 is a radially outwardly extending shoulder projecting from the proximal portion of main cylindrical body 106 of syringe assembly 102. [0075] As best illustrated in Figure 11 , syringe assembly 102 is received within the interior of housing 122. For example, during assembly of injection assist device 120, syringe assembly 102 may be inserted through the opening in the proximal end of housing 122. Syringe assembly 102 is secured in position by a ledge 112 formed in retaining extensions 178 and corresponding guide projections 114. Guide projections 114 are axially extending radially inward protrusions formed on the interior surface of housing 122, which together with retaining extensions 178 define activator channels 146 and plunger channels 148. In some embodiments, including the illustrated embodiment, retaining extensions 178 and guide projections 114 are shaped so as to define an opening of relatively wider diameter distally of ledges 112 than proximally of ledges 112, to allow syringe assembly 102 including radially outwardly projecting shoulder 108 thereof to be slid distally into housing 122. Some embodiments of injection assist device 120 are slightly larger in size than an injection assist device 20 configured to deliver the same volume of medicament, given the need to accommodate syringe assembly 102, including the outwardly projecting shoulder 108 thereof.

[0076] In the illustrated embodiment, narrow distal portion 104 of syringe assembly 102 contacts a syringe stabilizer 149, which is integrally formed or secured at the distal end of housing 122. In some embodiments, the shape of syringe stabilizer 149 is complementary to the shape of narrow distal portion 104 of syringe assembly 102 to facilitate the secure engagement of syringe assembly 102 within housing 122.

[0077] In the illustrated embodiment, needle 126 is pre-assembled together with the other components of syringe assembly 102 prior to assembly of injection assist device 120. In alternative embodiments, the needle could be secured to the other components of syringe assembly 102 after assembly of injection assist device 120, provided that a suitable mechanism (e.g. Luer-Lok™ fitting) is provided to securely couple the needle to the other components of syringe assembly 102. [0078] Plunger 132 is slidably received within main cylindrical body 106 of syringe assembly 102. Plunger 132 optionally has a seal (not shown) at its distal end made of rubber or soft plastic for the purpose of providing a sliding, sealing engagement with the interior surface of main cylindrical body 106. The friction between plunger 132 (including any seal, if present) and syringe assembly 102 retains syringe assembly 102 in place against ledge 112. In the illustrated embodiment, movement of plunger 132 in the proximal direction is prevented by power spring 168, which is received in cylindrical extension 166, and thus syringe assembly 102 is secured against movement in the proximal direction after injection assist device 120 has been assembled. In some embodiments, syringe assembly 102 is secured in place against ledge 112 and/or syringe stabilizer 149 by a suitable adhesive.

[0079] With reference to Figure 14, in the illustrated embodiment activator 124 has two activation prongs 156, each having angled activation surfaces 158. Each activation prong 156 is slidably received within a corresponding activator channel 146, to activate injection assist device 120 by axially and rotationally displacing release mechanism 134, in the manner described for release mechanism 34. In the embodiment of Figures 11-15, release mechanism 134 is provided by two plunger prongs 170 on plunger 132 (Figure 15). Plunger prongs 170 interact with retaining extensions 178 of housing 122 and activation surfaces 158 of activation prongs 156 to trigger injection assist device 120 in the same manner as discussed above with respect to the interaction of plunger prongs 70 with retaining extensions 78 of housing 22 and activation surfaces 58 of activation prongs 56 of injection assist device 20. The illustrated embodiment of injection assist device 120 has two plunger channels 148, which allow distal movement of plunger 132 to inject medicament when the device is triggered.

[0080] While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. To the extent that such modifications, permutations, additions, sub-combinations, and combinations thereof are not mutually exclusive, all are within the scope of embodiments of the present invention. Without limitation, examples of such modifications include:

• Although portions of injection assist device 20 have been described as being separate pieces, components of injection assist device 20 that do not engage in relative motion could be integrally formed. For example, medicament chamber 30 could be integrally formed with housing 22. Plunger 32 could be integrally formed with seal 64.

• The spring retainer for power spring 68 could be provided on end cap 40 rather than on plunger 32.

• The relative orientation of activation prongs 56, retaining extensions 78, and plunger channels 48 could be reversed, provided that the relative orientation of angled surfaces 58 and 60, and 80 and 60, are also reversed.

• Various optional features described with reference to injection assist device 20 could be used with or incorporated into injection assist device 120.

Claims

WHAT IS CLAIMED IS:

An injection assist device for automatically injecting a medicament into a subject once the device has been triggered, the device including a medicament chamber and a plunger for moving medicament from the medicament chamber through a needle in fluid communication with the medicament chamber, the device comprising:

a retaining mechanism for securing the plunger against movement in a distal direction when the device is in an armed configuration; and

an activator that slidingly and rotationally displaces the retaining mechanism when the device is triggered to allow distal movement of the plunger to move the medicament from the medicament chamber.

An injection assist device as defined in claim 1 , wherein the activator is slidable in a proximal direction to trigger the device when the device is pressed against an injection site of the subject.

An injection assist device comprising:

a housing;

a needle supported within and projecting from a distal end of the housing for injecting a medicament into a subject;

a medicament chamber within the housing in fluid communication with the needle;

a plunger disposed within the housing to move medicament from the medicament chamber through the needle when the injection assist device is triggered, the plunger being sealingly engaged with the medicament chamber; an activator slidingly engaged with the housing and slidable upon the application of a triggering force;

a release mechanism for initially securing the plunger in an armed position, the release mechanism being slidable and rotatable relative to the housing from the armed position into a triggered position when a triggering force is applied to the activator; and

an actuator for applying an injection force against the plunger. 4. An injection assist device as defined in claim 3, wherein the activator is slidable in a proximal direction upon the application of the triggering force. An injection assist device as defined in claim 3 or claim 4, wherein the actuator for applying an injection force against the plunger is configured to apply the injection force against the plunger in a distal direction.

An injection assist device as defined in any one of claims 3-5, wherein the activator comprises an activation prong that triggers the release mechanism when the triggering force is applied.

An injection assist device as defined in claim 6, wherein the housing comprises an activator channel on an interior surface of the housing, and wherein the activation prong is slidably disposed within the activator channel.

An injection assist device as defined in claim 6 or claim 7, wherein the proximal end of the activation prong comprises an angled activation surface.

An injection assist device as defined in claim 8, wherein the release mechanism comprises a plunger prong extending radially outwardly of a main body of the plunger, the plunger prong being releasably engaged with the housing when the device is in the armed state.

An injection assist device as defined in claim 9, wherein the housing comprises an axially extending channel for receiving the plunger prong to allow the plunger to slide in the distal direction relative to the housing when the device is triggered.

An injection assist device as defined in claim 10, wherein the plunger prong comprises an angled activation surface, and wherein the angle of the activation surface on the plunger prong is complementary to the angle of the activation surface on the activation prong.

An injection assist device as defined in claim 11, wherein the angled activation surfaces comprise smoothly angled surfaces.

An injection assist device as defined in any one of claims 9 to 12, wherein the

portion of the housing that engages the plunger prong when the device is in the armed state comprises a radially inward extension of the housing.

14. An injection assist device as defined in claim 13, wherein the activation prong comprises a securing surface for engaging with the radially inward extension of the housing to prevent rotational movement of the plunger relative to the housing until the activator is moved to a triggering position.

15. An injection assist device as defined in claim 13 or claim 14, wherein the

radially inward extension of the housing comprises an angled triggering surface at a proximal end thereof. 16. An injection assist device as defined in claim 15, wherein the angled triggering surface comprises an angle that is complementary to an angle of the activation surface of the plunger prong.

17. An injection assist device as defined in claim 16, wherein the plunger prong comprises a retaining prong.

18. An injection assist device as defined in claim 17, wherein the retaining prong comprises an angled surface for engaging the triggering surface on the housing. 19. An injection assist device as defined in claim 18, wherein the angle of the

angled surface of the retaining prong is complementary to the angle of the triggering surface.

20. An injection assist device as defined in any one of claims 11 to 19, wherein the angle of the activation surfaces is between about 15° and about 75°.

21. An injection assist device as defined in any one of claims 11 to 19, wherein the angle of the activation surfaces is between about 30° and about 60°. 22. An injection assist device as defined in any one of claims 11 to 19, wherein the angle of the activation surfaces is about 45°.

23. An injection assist device as defined in any one of claims 11 to 22, comprising three activation prongs for engaging with three corresponding plunger prongs.

An injection assist device as defined in claim 23, wherein the three activation prongs and the three plunger prongs are symmetrically disposed about a circumference of the injection assist device.

25. An injection assist device as defined in any one of claims 11 to 22, comprising two activation prongs for engaging with two corresponding plunger prongs.

26. An injection assist device as defined in claim 25, wherein the two activation prongs and the two plunger prongs are symmetrically disposed about a circumference of the injection assist device.

27. An injection assist device as defined in any one of claims 1 to 26, wherein the medicament chamber comprises a conventional syringe.

28. An injection assist device as defined in claim 27, wherein the conventional syringe is retained within the housing by engagement of a radially outwardly extending shoulder at a distal portion of the syringe with a ledge formed on the interior of the housing.

29. An injection assist device as defined in claim 28, wherein the ledge is formed in radially inward extensions of the housing that define the axially extending channel for receiving the plunger prong. 30. An injection assist device as defined in any one of claims 27 to 29, wherein a distal portion of the housing comprises a syringe stabilizer for supporting the conventional syringe.

31. An injection assist device as defined in claim 30, wherein the syringe stabilizer is complementary in shape to a distal portion of the conventional syringe.

32. An injection assist device as defined in any one of claims 1 to 31, wherein the activator comprises a distal portion for contacting the skin of a subject. 33. An injection assist device as defined in any one of claims 1 to 32, wherein the actuator comprises a coil spring.

34. An injection assist device as defined in claim 33, comprising a spring retainer. 35. An injection assist device as defined in claim 34, wherein the spring retainer comprises a cylindrical extension on a proximal portion of the plunger.

36. An injection assist device as defined in any one of claims 1 to 35, comprising a re-extension spring disposed between the housing and the activator to apply a distal force against the activator to push the activator to a resting position covering the needle.

37. An injection assist device as defined in any one of claims 1 to 36, comprising a radially outwardly projecting rim on the plunger and a radially inwardly projecting stop on an inside surface of the housing for stopping further movement of the plunger in the distal direction once a desired amount of medicament has been injected.

38. An injection assist device as defined in any one of claims 1 to 37, comprising a radially outwardly projecting rim on the plunger for engaging with at least a portion of the medicament chamber to stop further movement of the plunger in the distal direction once a desired amount of medicament has been injected.

39. An injection assist device as defined in any one of claims 1 to 38, comprising a retaining feature for preventing the activator from being ejected from the housing.

40. An injection assist device as defined in claim 39, wherein the retaining feature comprises an outwardly projecting hook provided on an internal portion of the housing, the hook being slidably engaged within a channel in the activator and a retaining surface at a proximal end of the channel.

41. An injection assist device as defined in any one of claims 1 to 40, wherein the needle has a length of 1/2 inch.

42. An injection assist device as defined in any one of claims 1 to 40, wherein the needle has a length of 3/4 inch.

43. An injection assist device as defined in any one of claims 1 to 40, wherein the needle has a length of 1 inch. 44. An injection assist device as defined in any one of claims 1 to 40, wherein the needle has a length of 1 and 1/2 inches. An injection assist device as defined in claim 42 or claim 43, wherein the overall dimensions of the device are the same as the overall dimensions of device as defined in claim 41. 46. An injection assist device as defined in claim 41 or 42, wherein the device is configured to provide an 0.2 mg dose of epinephrine upon activation.

47. An injection assist device as defined in aspect 43, wherein the device is

configured to provide an 0.4 mg dose of epinephrine upon activation.

48. An injection assist device as defined in any one of claims 43 to 45, wherein the device is configured to provide an 0.6 mg dose of epinephrine upon activation.

49. An injection assist device as defined in any one of claims 1 to 48, wherein the device is an auto-injector.

50. A method of injecting a medicament into a subject, the method comprising the steps of:

providing an injection assist device having a housing and an activator axially slidable therein;

placing the activator against an injection site of the subject;

pushing on the housing in a distal direction to cause the activator to slide proximally relative to the housing and to cause a needle at the distal end of the housing to be inserted into the injection site;

allowing the activator to displace a retaining member axially and rotationally to release a plunger of the injection assist device from an initially retained armed position to a triggered position; and

allowing an actuator of the injection assist device to move the plunger in the distal direction to inject the medicament into the subject.

51. A method according to claim 50, further comprising the steps of withdrawing the needle from the subject and allowing a second actuator to slide the activator in the distal direction to cover the needle. 52. A method according to claim 51 , further comprising the step of securing a needle end cap over the needle after the needle has been withdrawn from the subject. An injection assist device substantially as described and illustrated herein.

A method of administering an injection using an injection assist device substantially as described and illustrated herein.

An injection assist device or a method of using same comprising any new, inventive useful features, combination of features, or subcombination of features, described or clearly inferred herein.