Apparatus and method for rapid auto-injection of medication

An auto-injector for rapid delivery of a bolus of injectable medication has a generally flat, sealed housing with small peripheral dimensions, approximating those of a credit card. A syringe, configured to be contained within the flat housing is pre-filled with the medication. The housing contains a mechanism that, when triggered, automatically drives the syringe and needle forwardly to an injection position and then continues to compress the volume of the syringe to effect rapid injection. The forward injection end of the device includes an actuator that also conceals and protects the needle at all times and, prevents post-injection hazards. The flat faces of the device have graphic symbols and other visual indicia relating to the operation and condition of the device. The device enables a simple three-step operation that reduces the risk of improper use.

FIELD

The invention relates to portable auto-injectors for rapid, automatic injection of a measured dose of medication.

BACKGROUND

Certain medical conditions require immediate injection of medication. The condition requiring such treatment may result from a variety of causes. Among the most serious of those conditions is anaphylaxis (a severe allergic reaction) that, in many cases, can become fatal within minutes if left untreated. Among the numerous allergens that may cause anaphylaxis are insect bites, various chemical substances and foods. Food products having even small quantities of peanuts, seafood or milk products can, in some individuals, induce severe, potentially lethal reactions. In foods, the allergen may be “hidden”, that is, the food, unknowingly, may contain a minute trace of an allergenic ingredient or may have been exposed to the allergenic ingredient during its processing. When anaphylaxis occurs, often there is insufficient time for the patient to reach a hospital or other trained and equipped medical personnel.

Individuals known to be at risk for anaphylactic reaction typically are advised to carry, at all times, an auto-injection device adapted to inject a bolus of epinephrine. The ability to inject the epinephrine immediately can be a matter of life or death. Notwithstanding the severe risk involved, there is evidence that a large proportion of the population that should be carrying such a device, in fact, does not. At least one study indicates that fewer than 30% of patients at risk of anaphylaxis carry the device at all times. See Goldberg A, Confino-Cohen R., “Insect Sting-Inflicted Systemic Reactions: Attitudes of patients With Insect Venom Allergy Regarding After-Sting Behavior and Proper Administration of Epinephrine”,J Allergy Clin Immonol2000; 106:1184-9. Food based allergies are reported to cause anaphylactic reactions resulting in 30,000 trips to the emergency room and 150 to 200 deaths per year (www.foodallergy.com). The main factor contributing to a fatal outcome is the fact that the victims did not carry their emergency kit with adrenaline (epinephrine). See Wuthrich, B., “Lethal or Life Threatening Allergic Reactions to Food”,J. Investig Allergol Clin Immunol,2000 March-April, 10(2):59-65. Moreover, even for those individuals that are required to carry such a device, it has been reported that a large proportion (as much as two-thirds) are insufficiently familiar with its use and operation. See Sicherer, S. H., Forman, J. A. , Noone, S. A., “Use Assessment of Self-Administered Epinephrine Among Food-Allergic Children and Pediatricians”,Pediatrics,2000; 105:359-362. Only 25% of physicians, in one study, were able to properly demonstrate the use of the device. See Grouhi, M., Alsherhri, M., Hummel, D, Roifman, C. M., “Anaphylaxis and Epinephrine Auto-Injector Training: Who Will Teach the Teachers?,Journal of Allergy and Clinical Immunology1999 July; 104(1):190-3. It has been estimated that as many as forty million individuals in the United States are at risk of anaphylaxis. See Neugut, A. I., Ghatak, A. T., and Miller, R. L., “Anaphylaxis in the United States: An Investigation into its Epidemiology”,Archives of Internal Medicine2001 Jan. 8; 161(1):15-21.

Perhaps the most common automatic emergency epinephrine injection device is commercially available from DEY, Inc. of Napa, Calif. under the trade designation EpiPen. The EpiPen device, believed to be described in U.S. Pat. 4,031,893, is designed to inject rapidly an adult dose of about 0.30 milligrams of epinephrine. The device is generally tubular and, including its tubular container, is about six inches long and nearly one inch in diameter. The device is relatively bulky and requires several manipulative steps in its use. Where a patient may only actually use the device infrequently, there may be some confusion in performing the required manipulative steps, particularly when the individual experiencing an anaphylactic reaction may be in a state of near panic. Although the device includes written instructions on its cylindrical surface, they may not be easily read, particularly under the stress of emergency circumstances. The manner in which the EpiPen is to be used is not readily and intuitively apparent without reading the text of the instructions on the cylindrical sleeve. Should it be necessary for someone other than the patient (e.g., a bystander) to administer the medication, for example, if the patient has gone into shock, the person called on to administer the medication may not know how to operate the auto-injection device. Consequently, precious time may be lost, increasing the risk to the patient. Additionally, after the device has been used to effect an injection, its hypodermic needle remains exposed, presenting post-injection hazards. Among such hazards are those associated with blood-born diseases such as HIV and hepatitis B and C or, when some of the medication remains in the device after injection, the risk of delivering some of the residual medication as a consequence of an accidental needle stick.

It would be desirable to provide a more compact, low profile, easily used auto-injector for rapid transcutaneous administration of a predetermined dose of medication.

SUMMARY

Our single-use, auto-injector for rapid delivery of a bolus of medication is configured to have a generally flat sealed housing with peripheral dimensions approximating those of a credit card to facilitate the ease and convenience of carrying, handling and using the device. The housing contains internal components configured and arranged to be in a generally flat array and to operate within the generally flat confines of the housing. The internal components include a syringe that is pre-filled with the selected injectable medication, the syringe including a syringe body and a hypodermic needle. The syringe is arranged to be moveable from a retracted, pre-injection position in which the device is stored, to an extended, injection position in which the needle extends out of the housing to penetrate tissue. The syringe itself is configured to be containable within a flat virtual envelope. A needle shield also may be carried by the housing to cover and enclose the hypodermic needle at all times before, during and after injection, so that the sharp tip of the needle is never exposed. The shield also may serve as an actuator, responsive to being pressed against the injection site to enable the needle to be driven from its retracted position to its injection position, first to pierce the patient's skin to the desired depth and then to inject automatically and rapidly a measured bolus of medication into the patient. When the device is actuated, the syringe is released from its retracted position to enable a self-contained power source first to drive the syringe toward the injection position and then to effect the injection of the medication. After injection, as the device is withdrawn from the patient, the needle shield automatically extends to a position to cover the needle. The device automatically locks the needle shield in its extended, needle-protective position. In another aspect, the generally flat configuration of the device provides ample space on which relatively large, easily understood, pictograms can be placed, graphically showing the manner of using the device or for providing other information.

The auto-injector includes a cover that is secured to the housing to contain and seal the injection end of the device, including the needle shield, during storage and before use. The cover is sealed to the housing and protects the device from inadvertent actuation. It must be removed in order to permit injection which is effected by then simply pressing the needle shield against the patient's skin. The cover may be transparent to enable the actuating member to be seen. The device may include a removable tamper-evident seal between the cover and the body of the device to further assure sterility and protection of the device before use.

It is among our general objects to provide a compact, portable, low-profile, safety, single use, auto-injector for rapidly administering a bolus of injectable medication and methods for rapid self-administration of medication. Other objects, advantages, aspects and features will be apparent to those skilled the art from the following, more detailed desciption.

DETAILED DESCRIPTION

FIGS. 1-6illustrate a compact, low profile, auto-injector that includes a generally flat housing10. The housing may be defined by a pair of mating, separately formed housing sections, including a front section12and a back section14. The front and back housing sections12,14may be formed from any appropriate material having sufficient strength to serve as a protective housing for the internal components of the device. The housing sections may be made from a thin injection molded metal or high pressure casting or from various polymers or engineered materials having sufficient structural and engineering characteristics, including rigidity and toughness, to insure the integrity of the internal components. The internal surfaces of the housing sections12,14may be formed to include a number of walls and sockets that serve to cooperate with the internal components of the device to maintain the components in place as well as to guide movable components along their intended paths of movement.

The auto-injector may be considered as having a rear end16and a forward end18and a longitudinal axis extending between the ends. The device is intended to be held by its rearward portions, with the forward end18being pressed against the patient's skin, such as against the thigh. When triggered, the device causes the injection needle to emerge, suddenly, from the front end and effect injection of the medication bolus.

A molded safety cover20is fitted onto the forward end of the housing10. The safety cover20maintains the sterility of the internal components and also prevents inadvertent actuation of the device. The safety cover20must be removed from the device before it can be used. The cover20preferably is formed from a moldable polymeric material having sufficient strength to protect the front end of the housing even under rough conditions. The material also should be selected to enable the formation of a thin, tearable connector by which a peel-away strip11may be attached to the body of the cover. The cover20may be transparent to enable the forward end of the housing including an actuator, described below, to be visible without removing the cap. The device is used in a simple three-step process, first by simply removing the peel-away strip11, then gripping the rear end with one hand while removing the safety cover20with the other hand, and then pressing the exposed forward end of the device against the injection site. The outer surface of the housing10may be provided with overmolded elastomeric grips28,30having frictional characteristics for holding the device securely in one hand. The elastomeric material of the grips28,30may be provided with an appropriate filler to enable the device to glow in a dark environment.

FIGS. 1A,1B,1C illustrate, in enlarged detail, the configuration of the housing10and the manner in which it interacts with the cover20and peel-away strip11. Each of the front and back sections12,14of the housing is formed with a first circumferential groove13and a second circumferential groove15located close to but forwardly of the first groove13. The first groove13is intended to receive a latch portion17of the strip11(FIG.1C). The second groove15is receptive to a compressible member, such as a molded gasket or O-ring19. The peel-away strip11may be formed integrally with the cover20, with the peel-away strip11being defined by a groove21formed circumferentially about the cover. The groove21, in turn, defines a thin circumferential connector23. The material of the cover20and peel-away strip10preferably is selected to be of a suitable polymer capable of protecting the forward end of the housing while also being tearable manually at the thin neck23. A tab25preferably is integral with and extends from the peel-away strip11to facilitate gripping and tearing of the strip. The cover20is assembled with the housing simply by inserting the forward end of the housing10into the rearwardly facing opening of the cover. As the peel-away strip11advances rearwardly toward the first groove13, it rides over the compressible gasket19. The lower, rearward facing edge of the locking element17preferably is beveled, as at27, to facilitate advancement of the peel-away strip11over and past the gasket19. When the lock portion17of the peel-away strip11reaches the first groove, it snaps into the groove13, preventing the cover from being removed until the strip11has been peeled away. When the device is in its stored configuration (FIG.1C), the compressed gasket19provides a seal between the inner surface of the cover20and the outer surface of the housing10to provide a barrier against contamination.

The flat configuration of the housing enables each of the front and back housing sections12,14to receive a label. The labeling area of at least one of the sections, e.g., the back section14, is of sufficient size to receive graphic images such as pictograms illustrating use of the device. As shown inFIG. 3, the label22A has three pictograms,29,31,33illustrating, respectively, removal of the peel-away strip11, removal of the cover and pressing the forward end against the injection site. The use of such graphics enables even one unfamiliar with the device to understand immediately how it is used.

The front and back sections12,14of the housing10may be secured together in a manner compatible with the particular materials from which the housing is made. For example, if the housing is made from an injection molded or cast metal, the sections may be secured together with screws35(FIG. 7) or an appropriate adhesive. The peripheral portions of the front and back sections12,14, may be sealed by interposing a thin gasket37between the facing surfaces of the peripheral walls of the housing sections. The gasket or O-ring19should maintain a seal where it contacts the thin gasket37. Should the front and back housing sections be formed from a plastic or engineered material, the sections12,14may be sealed by sonic welding, adhesives or other bonding agents, as appropriate.

Each of the front and back housing sections12,14may be provided with a window24,26, respectively, through which the condition of the medication in the syringe can be observed. For example, in the case of epinephrine, the presence of dark brown color or a precipitate in the medicine indicates that the strength of the medication has become reduced or that it has lost its therapeutic function, signaling that the medicine is not reliable and that the device should be replaced. The window should be formed from a material, or should be coated, to prevent exposure of the medication to quantities of ultraviolet light that might adversely effect its medicinal characteristics. When the device is used with medications for which visual inspection is not particularly critical, the window may be modified or omitted. Omission of the window provides for additional flat surface on which labels may be placed appropriate to the particular medication or intended use of the device.

The device preferably is dimensioned to be held in one's palm and may have peripheral dimensions approximating those of a conventional credit card. In a preferred illustrative example, the housing may be about 3.25 inches long, and about 2.0 inches wide. The thickness of the device is substantially less than either of the length or width and, in the preferred illustrative example, may be of the order of 0.25 inch thick. The device, so dimensioned, has a generally flat appearance. It is carried easily in ones pocket or purse without feeling bulky or uncomfortable thereby increasing the likelihood of it being carried on one's person and being available, if needed. It should be understood, however, the foregoing dimensions are illustrative only and that the precise dimensions and peripheral shape of the device may be varied as long as the device maintains its compact configuration and is not made so large as to defeat its compact and portable characteristics.

The term “flat” when used in this specification to describe the housing of the device is intended to mean a configuration that can be confined in a virtual three dimensional envelope having a length, a width, and a thickness, and in which the thickness is substantially less than each of the length and width, with each of the length, width and thickness being measured along orthogonal directions. Although the embodiments described in this specification may be considered as having a generally rectangular peripheral configuration, other, non-rectangularly configured housings may be employed that have orthogonally measured length, width and thickness of a flat virtual envelope, as defined. It also should be understood that “flat” is not intended to be limited to precisely planar in a mathematical sense.

Although the most preferred embodiment has peripheral dimensions approximating those of a credit card (2.125″×3.375″) and a thickness of about 0.25inch, the dimensions of the device may be varied while still maintaining the flat characteristic described in the specification. Preferably, a range of lengths between about 2.8 to about 3.8 inches may be employed with a width in the range of about 1.7 to about 3.5 inches. The thickness of the device may be between about 0.20 to about 0.75 inch.

FIGS. 7-15illustrate the internal components of an exemplary device embodying aspects of the invention. The device may be considered to include two longitudinally sliding assemblies, including an actuator assembly32and a syringe carrier assembly34. The actuator assembly32(FIG.9), which may be formed from molded plastic mirror-image mating sections (seeFIG. 8) in the same manner as the mating housing sections12,14, includes a generally flat needle shield36at its forward end and a trailing portion, such as a pair of arms38extending rearwardly from the shield36. The needle shield36has an internal needle passage37adapted to contain the forward end of the needle. The passage terminates, at its forward end at an opening39. The trailing end of each arm38includes a living hinge40by which a finger42is flexibly attached to the arm38. Each finger42includes a radially inwardly extending detent44that cooperates with the syringe carrier assembly34in a manner described below. The laterally outward surfaces of the arms38are slidably guided by a pair of guide walls46, formed integrally with the front and back housing sections12,14, and guide surfaces48formed at the forward end of the housing10. The guide surfaces48define a forward opening49in the housing through which a forward portion of the needle shield36projects. The actuator assembly32is retained in the retracted position shown inFIG. 8by a pair of releasable arm locks50that are mounted interiorly of the housing and releasably engage forward apertures51formed in the arms38of the actuator assembly32(FIGS.8and9). When the actuator assembly32is in its retracted position (FIG.8), the forward portion of the needle shield36projects slightly beyond the forward end15of the housing10. When the cover20is separated from the housing, the forward end of the needle shield36is exposed and serves as an actuator to initiate operation of the device, when pressed against the patient's skin. The actuator32, or at least the portion of the needle shield36that projects forwardly of the housing before the device is actuated, may be formed from or provided with a label that has a visually distinct appearance from that of the housing, for example, by providing it with a red color or other warning indicia. When the cover20is transparent, the distinct forward portion of the shield is visible through the cover enhancing an understanding of the operation of the device merely from its appearance.

The actuator assembly32is biased in a forward direction by a pair of longitudinally disposed side compression springs52. One end of each side spring52is captured in a socket54defined by walls49,53and the sidewalls55of the housing molded as part of the housing sections12,14. The other, forward, end of each side spring52is captured in a socket56(FIG. 11) defined by each of a pair of outriggers58that extends laterally from its associated arm38. The outermost end of each outrigger58terminates in a guide member60that slides along and is guided by a longitudinally extending surface62of the sidewall formed by the mated housing sections12,14. When the device is in the storage configuration shown inFIG. 8, the side springs52are substantially, but not completely, compressed. The springs52can be compressed further in order to permit the entire actuator assembly32to move slightly proximally to trigger the injection procedure, as described below.

The actuator assembly32is releasably maintained in the retracted configuration shown inFIG. 8by the releasable arm locks50. As shown in enlarged detail inFIG. 10each arm lock50has a retained end62that may be U-shaped and is captured in a socket64formed by cooperative walls of each of the front and back housing sections12,14. The arm locks50may be formed from a suitable plastic having characteristics that will enable it to perform its spring function. Each arm lock50includes an extension66that functions in the manner of a resilient leaf spring. The end of each extension66has an inwardly projecting finger68that extends laterally inwardly through a distal aperture51formed in its associated arm38of the actuator assembly32. The extension66includes a flat section72that engages squarely a surface70(FIG. 11) that defines the aperture51in the arm38. The tip of the finger68extends inwardly beyond the inner surface74of the arm and defines an inclined, wedge surface75that, when engaged, trips the locks50and as described below, releases the arms38, permitting the entire actuator assembly32to be driven distally under the influence of the side springs52. The arm locks50are tripped automatically when the injection needle has penetrated the patient's skin to the desired depth and the injection has been made.

The syringe carrier assembly34includes a syringe carrier76and a syringe82, pre-filled with a selected injectable medication. For the syringes described, the syringe carrier76may be U-shaped, defined by an upper wall78and a pair of downwardly extending sidewalls80. In this exemplary embodiment, the syringe82has a flat configuration and is defined by a flat plunger-type device comprising a cup-like container84having an open end86that receives a plunger88that carries an injection needle90. The syringe carrier76is connected securely to the syringe, for example, by dimensioning the container84and carrier76to provide a snug friction fit which may be supplemented by lugs85extending from the carrier sidewalls80that engage the forward edge of the container.

In a device in which the medication to be contained in the container84may be epinephrine, the container84preferably is formed from glass and is transparent so that its front and back faces92,94(FIG. 15) may serve as windows. The windows are located to be aligned with the windows24,26on the front and back housing sections12,14, when the device is in its retracted configuration (FIG.8). In that manner, the user may observe the contained liquid through the windows to determine visually its condition. This is particularly important with a medication which changes color or forms a precipitate when its medicinal effectiveness has been reduced or lost. It should be understood that, although use of a glass container84is desirable when the medication is epinephrine, the container84may be formed from a variety of other materials that are compatible with the particular medication to be contained. In this embodiment, the container84has a flat configuration in which the thickness T of the container is substantially less than either of its length L or width W (seeFIGS. 14,15). The container84has front and back walls92,94joined by a peripheral wall96that is securely engageable by the syringe carrier76. The open end86of the container faces forwardly and is closed by the flat plunger88that is slidable into the container84. The plunger88engages the internal surfaces of the front and back walls92,94as well as the side portions98of the peripheral wall96. The outer surface of the plunger should be slidably sealed to the container as by providing the plunger with one, and preferably several, wiping ribs100that extend about the plunger88to engage with the internal surfaces of the walls92,94,96(FIG.16). The peripheral wall may be radiused, if desired, to facilitate an enhanced seal between the container84and plunger88. The plunger itself may be solid or hollow, depending on the volume of medication to be contained and should be formed from a material that is compatible with the contained medicine, such as rubber or other compositions of the type used in conventional tubular syringes. The hollow plunger illustrated inFIGS. 14 and 15may be considered as having front and back walls102,104and a peripheral wall106. The rear end108of the plunger88is open to communicate with the interior of the container84.

In this embodiment, the forward end of the plunger88includes a needle carrier110by which the injection needle90is held in spaced alignment with a septum112that forms a seal at the forward end of the plunger (FIG.13). The septum112completely closes the forward end of a passage114that extends through the wall of the plunger and communicates with the interior volume of the syringe. The needle carrier110may include a pair of longitudinally collapsible, forwardly extending, accordion-like supports116that may be biased in a distally extended configuration, by a compression spring118. The double-ended needle90may be secured to an anchor122that can be embedded, together with a portion of the needle, in the needle support120. The sharp rear tip of the needle should be non-coring, and is supported in slightly spaced relation to the forward side of the septum112. The sharp rear end of the needle90is maintained in spaced relation to the outer surface of the septum112by the compression spring118that extends between the septum112and the needle support120. When the needle is in flow communication with the syringe body, the flow passage from the syringe body, into and through the needle should be unobstructed and sufficient to enable rapid delivery of the bolus of the medication. The rear end of the compression spring124may be retained in place by a boss126formed about the forward face of the septum112and adapted to engage the rear end of the compression spring124. The forward end of the spring124is tapered and bears against the needle support, with the spring surrounding the forward end of the needle90.

In this description and in the claims of this specification, the term “syringe” is intended to mean a syringe body adapted to contain injectable medicine in which the body has an interior collapsible volume with a hypodermic needle carried by the syringe body and being connected or connectible to the interior chamber to enable mediation to be injected from the container through the needle into the patient. The above definition of “flat” when used to describe the syringe82is intended to have the same meaning as that discussed above in connection with the configuration of the housing, namely, as referring to a syringe body containable within a virtual envelope having a length, a width, and a thickness and in which the thickness is substantially less than each of the length and width, with each of the length, width and thickness being measured along directions orthogonally related to the others. Thus, the described arrangement of the syringe82may be considered to comprise a flat syringe. Although two specific configurations of flat syringes are described in this specification, it should be understood that other syringe configurations, containable in the flat housing, may be employed in the practice of the invention.

As shown inFIGS. 8,11and12, the syringe assembly34is restrained in its retracted position by engagement of a pair of latches128formed as part of the syringe carrier76. Each of the latches128extends in a laterally outward direction and engages the detent44of one of the fingers42of the actuator assembly. Each of the fingers42is biased into locked engagement with the latch128by a latch spring130. The latch spring130may include a base portion132which is secured in a socket134molded into the housing sections12,14, and a resilient member136that extends from the base132into engagement with the outwardly facing surface138of the finger42. The free end140of each finger42may be beveled, as indicated at140. The beveled free end140is biased into engagement with a wall142that includes a camming surface144. The camming surface144is oriented with respect to its associated finger42to guide the finger42to pivot outwardly (clockwise as seen inFIG. 12) about the hinge40as the actuator assembly32, including the finger42, is moved slightly to a more retracted, proximal position. Such movement, initiated by pressing the forward end of the actuator against the injection site causes the fingers42to pivot outwardly, disengaging each detent44from its associated latch128, and freeing the syringe assembly34for forward movement. The syringe assembly is biased for such movement by an injector compression spring146. The injector spring146is retained, at its rear end, in a socket148formed integrally with the housing sections12,14. The forward end of the spring146bears against the upper wall78of the syringe assembly34where it is held by providing the upper wall with a retention boss or socket150engageable with the spring112(FIG.8). The injector spring for some applications, especially those of an emergency nature, should develop enough force to drive the needle through clothing, in addition to tissue.

The injector spring146is configured so that with the actuator and syringe assemblies32,34in the locked configuration (FIG.8), the injector spring112is capable of a small amount of further longitudinal compression. The extent of additional longitudinal compression should enable the actuator and syringe assemblies32,34to be retracted sufficiently to withdraw the detents44from locked engagement with the latches128. When the latches128have been released, the syringe assembly34is released and is driven immediately and forcefully in a forward direction by the injector spring146. The syringe assembly34is guided in that movement by engagement of the outer surfaces152of its sidewalls80with the inner surfaces74of the arms38of the actuator assembly32.

As the syringe assembly34is driven forwardly, the sharp, forward tip of the injection needle90projects longitudinally through an aperture154in the needle shield36and beyond the forward end156of the needle shield36. At this stage in the operation of the device, the forward end156remains pressed firmly against the user's skin and the force of the injector spring146will drive the needle90into the patient's tissue to an intended depth. The selected depth of needle penetration will depend, in part, on the type of medication to be injected and whether it is to be an intramuscular or subcutaneous injection. The depth of needle penetration is determined by the length of the needle and the needle shield as well as location of the needle when its forward advancement is terminated. In this embodiment forward movement of the needle terminates when the needle support120engages the rear face158of the needle shield36. Throughout the advancement of the syringe assembly34, the actuator assembly32remains locked in place by engagement of the arm locks50with the forward sockets51in the arms38of the actuator assembly32.

When the needle90has penetrated the tissue to the intended depth, the needle support120will have bottomed on the rear face158of the needle shield36and the needle carrier110will begin to collapse, advancing the syringe body, including the septum112, toward the rear end of the needle. Continued advancement causes the septum112to impale itself on the needle90, establishing flow communication between the needle and the interior of the syringe. When the supports116have collapsed, the plunger88can no longer advance forwardly. The container84, however, is free to continue forward advancement sliding over the plunger, under the continued force of the spring146and, in so doing, the internal volume of the syringe is compressed, causing ejection of a bolus of medication through the needle into the patient.

Different medications, of course, will require different doses. Additionally, depending on the nature of the medication, it may be desirable for the syringe to contain a greater volume of medication than the actual volume of the dose to be injected. For example, when the medication is epinephrine, (1:1000) an adult dose is considered to be 0.3 ml. The stability of the epinephrine, however, is improved when it is stored in a larger volume of about 2.0 ml. Therefore, the extent to which the internal volume of the syringe can compress may be limited to assure injection only of the desired dose. The volume of the injected dose may be limited by limiting the extent to which the internal volume of the syringe can be compressed. This can be accomplished, for example, by providing an abutment surface160internally of the housing. The abutment surface160is located to be in alignment with a forwardly facing surface162at the end of each of the container carrier sidewalls80. When the ends162of the sidewalls80have engaged the abutment surfaces160, forward movement of the container84is terminated, thus terminating the ejection stroke. Another approach to limiting the extent to which the syringe volume can be compressed is to dimension the container84and plunger88so that the rearward face108of the plunger bottoms out on the inner face of the rear portion109of the peripheral wall of the container84.

Throughout the release of the syringe assembly34from its locked, restrained position until the time that the bolus of medication has been injected into the patient, the entire device is pressed firmly against the injection site. Throughout the time that the needle begins to protrude from the forward end156of the shield36until the time that the device is fully withdrawn from the injection site, no portion of the needle is visible or exposed.

As the syringe assembly34is driven forwardly by the injector spring146, the actuator assembly32is restrained from moving forward relative to the housing10by engagement of the arm locks50with the arms38. Engagement of the arm locks50with the arms38also serves to limit the extent of rearward travel of the actuator assembly during the initial triggering operation, as the forward surface156of the shield36is pressed against the injection site. As the syringe carrier76and syringe82approach the end of the injection stroke, the protruding ends68of the arm locks50are engaged by a portion of the container assembly, such as a portion of the lower ends160of the sidewalls80of the container carrier76, thereby tripping the arm locks50to disengage from the arms38and permit the actuator assembly32to be driven forwardly with respect to the housing10under the influence of the side springs52. This assures that the forward end156of the needle shield36will be continually and automatically pressed against the patient's skin as the device is withdrawn from the patient. Consequently, after the injection has been completed, withdrawal of the device from the patient enables the side springs52to simultaneously and progressively cause extension of the needle shield36to cover and completely contain the needle90. The actuator assembly32and its needle shield36are permitted to move forwardly sufficiently to assure that when the device has been withdrawn to the point that it no longer contacts the skin, the needle is completely covered by the shield36.

The outwardly facing surfaces164of the needle shield36that project beyond the forward end15of the housing10after the device has been used also provide a wide, flat area receptive to labeling165(FIG. 7) or other imprint with sharps biohazard warning symbols166(FIG.8). The biohazard warning symbol166preferably is placed on the portion168of the more rearward surface of the needle shield that is exposed only when the shield has been extended to its post-injection, needle covering position. In order to assure that the needle shield cannot be inadvertently depressed to expose the needle after the device has been used, another detent aperture170is formed in each of the arms36rearward of the apertures51, to receive and engage the latch50when the actuator assembly32and needle shield36have been projected to fully cover the needle90. Thus, once the needle shield36has been extended to cover the needle, it is automatically locked in that protective configuration and no further steps are required in order to prevent accidental post-use needle stick.

FIGS. 17-22illustrate the above-described device in various stages of operation. After the peel-away strip and cover20have been removed (FIG. 17) and the needle shield36of the actuator assembly32has been pressed against the patient's skin (FIG.18), the syringe carrier will be released from its latched position to be driven distally under the influence of the drive spring112with sufficient force to cause the needle to pierce the skin and penetrate the tissue to the intended depth (FIG.18). When the needle platform120abuts the surface158, the sharp forward end of the needle will have penetrated the patient's tissue to the intended depth. The continued influence of the drive spring146drives the syringe carrier and the syringe, as a unit, forwardly, to cause the septum112to impale itself on the sharp rear end of the needle, communicating the lumen of the needle with the medication contained in the syringe. The supports116collapse until forward movement of the plunger84has terminated. The continued influence of the drive spring146will advance the syringe carrier and container84forwardly over the then-stationary plunger, collapsing the volume within the syringe and causing a bolus of the medicine to be injected into the patient (FIG.26). Injection terminates when the compression of the syringe volume is terminated. As the injection stroke approaches its termination the arm locks50are tripped. With the actuator assembly arms38freed, the actuator assembly will advance forwardly relative to the housing under the influence of the side springs52, as the device is withdrawn (FIG.21). The needle shield36will be extended to cover and protect the forward end of the needle, with the arm latches50dropping into the rear apertures170to lock the actuator assembly32and needle shield36in the distally extended, needle protecting configuration (FIG.22). With the needle shield extended in its distal, locked position, the biohazard indicia166on the flat faces of the shield are exposed prominently to serve their warning function.

It should be understood that the use of a compact, portable, pre-filled, single use auto-injector is not limited to administration of medicine for treatment of anaphylactic reaction. There are many medical conditions and circumstances that may make desirable a readily available, easily carried, injectable medication that may be administered by oneself or by another person without formal medical training. The medication to be injected may be one serving somewhat of an emergency function, such as administration of epinephrine, morphine, atropine, cardiotonic medication, anti-seizure medicines as for treatment of status epilepticus, antitoxins, anticoagulants and the like. Other medications deliverable by auto-injector may be more in the nature of convenience, such as administration of anti-migraine medication (e.g., sumatriptan or ergonovine), vaccines, growth hormone, antibiotics, injectable vitamins, and contraceptives, among others. Injectable medications may also include anticholinergic medication (atropine), anti-arrhythmics (e.g., lidocaine, amiodarome), drugs for the treatment of multiple sclerosis (e.g., interferon), cholinomimetics (e.g., neostigmine), anti-nausea and gastrointestinal stimulants (e.g., metoclopramide), diuretics (e.g., furosemide), sedatives and hynotics (e.g., hydroxyzine), anti-psychotic agents (e.g., haloperidol), analgesics (e.g., morphine), hypocalcimic drugs (e.g., calcitonin), corticosteroids (e.g., methyl prednisolone), anxiolytics (e.g., diazepam), insulin, erythropoietin, colony stimulating factor (e.g., Filgrastim), and anti-vertigo drugs (e.g., dimenhydrinate), anticoagulants (e.g., heparin and low-molecular-weight heparin), antidiuretic hormone, fusion inhibitors (e.g. T-20), monoclonal antibodies and interlukens. Other possible injectable medications will be apparent to those familiar with pharmaceuticals and the indications for their use.

FIGS. 23-29illustrate another embodiment of the device in which the syringe includes walls that are collapsible in an accordion-like fashion. In this embodiment, the actuator assembly and syringe carrier may be considered as substantially the same as in the previously described embodiment. For convenience, elements in this embodiment that are identical to those in the previously described embodiment will be designated with the same reference numeral. In those instances where the device is essentially the same, but with slight modifications, either apparent from the drawing, or described, the reference numeral will be the same with a prime mark (′). For those components that warrant more detailed description, new reference numerals are used.

It may be noted that in this embodiment, the housing includes a peripheral configuration in which the rear portion is wider than the forward portion. It should be understood that although the previously described embodiment had a housing with peripheral dimensions approximating a rectangle, it may be desirable in some instances to configure the housing so that its rear end is wider or more narrow than its forward end. Indeed, the configuration of the housing may include non-rectangular peripheral geometries that, nonetheless, are flat and are containable within the defined flat virtual envelope.

In this embodiment, the syringe200may be considered as having a relatively rigid, shape-retaining rear portion202adapted to fit securely within the generally rectangular opening defined by the U-shaped container carrier76. The rearward portion202of the syringe200may be provided with a pair of windows201,203on its front and rear surfaces, as by forming the syringe body from a transparent material such as polyethylene terephthalate (PET). The windows are located to be aligned with the windows24′,26′ on the front and rear housing sections12′,14′, when the device is in its retracted configuration (FIG.25). The syringe may be formed, as by blow molding. The syringe body has a flat configuration, as defined.

The forward portion204of the syringe200, in this exemplary embodiment, is collapsible and may be molded or otherwise formed in a collapsible bellows arrangement. The forward portions of the syringe200includes a sufficiently sturdy bottom wall206to provide a secure mount for a hypodermic needle90′. The needle208extends longitudinally in a forward direction and terminates in a sharp tip. The medication is pre-loaded and sealed within the syringe body200when the device is fabricated so that it is not exposed to the lumen of the injection needle208until the device has begun its operation. To that end, a pressure rupturable membrane210may be disposed within the syringe200over the rear end of the needle90′ (FIG.26). When, as described below, the pressure within the syringe200has increased to a sufficient predetermined level, the membrane210will rupture to immediately communicate the interior of the syringe200with the lumen of the injection needle90′. It should be understood that other sealing arrangements may be employed, including arrangements in which the proximal end of the hypodermic needle pierces a sealing septum just before injection is to be completed as described in connection with the previous embodiment.

After the needle90′ has penetrated the tissue to the intended depth, the continued forwardly directed force of the injector spring146initiates longitudinal collapse of the syringe200and decrease of its internal volume. The rupturable membrane210that seals the container will burst when the pressure within the container has reached a predetermined design limit. When the membrane210ruptures, communication between the interior of the syringe and the lumen of the hypodermic needle90is established such that continued collapse of the syringe200under the influence of the injection spring146will force the liquid medication through the needle90into the patient. As with the previously described embodiment, the force of the injector spring146is selected to be sufficient to cause the desired volume of medication to be injected into the patent in a rapidly delivered bolus. Where the medication to be delivered is such, as with epinephrine, as to require a larger volume to be contained within the syringe, the extent to which the syringe200is compressed, can be limited by engagement of the forward end162of the syringe carrier34with the abutment surface160on the actuator assembly32′.

FIGS. 27-31illustrate the above-described device in various stages of operation.FIG. 27illustrates the device when it has been pressed against the patient's thigh to push the actuator assembly rearwardly into the housing10to an extent sufficient to release the latch128′ to initiate the needle penetration phase.FIG. 28illustrates the components of the device when the injection spring146has advanced the syringe assembly distally to the point in which the forward end of the syringe body200(e.g., the bottom wall206of the bellows in this embodiment) is advanced into engagement with the abutment surface158′ of the actuator assembly. At this point, the needle208will have been projected beyond the forward end156′ of the needle shield36′ and will have penetrated into the patient's tissue to the predetermined depth and the injector spring146and syringe carrier will continue to advance to the stage illustrated in FIG.29. During the advancement to theFIG. 29stage, the bellows204is compressed, first causing a build-up of pressure within the syringe body sufficient to effect communication with the lumen of the needle208and then to forcefully inject the bolus of medication through the needle and into the patient. As the injection progresses under the influence of the injection spring146, the forward ends of the syringe carrier engages the finger68of the latches50to urge the latches outwardly, disengaging the fingers from the arms.FIG. 30illustrates the device after the injection phase has been completed, with the latches50having been tripped. When the latches50disengage from the arms, the actuator assembly34is released and is driven forwardly by the springs52, causing the rearward portion of the needle shield36′ to project beyond the forward end of the housing. The forward end156′ of the needle shield is maintained in contact with the patients skin throughout that motion so that the shield progressively covers the needle208as the housing10′ is drawn away from the skin. That motion continues until the device has reached the stage as shown inFIG. 31in which the needle shield36′ has extended fully to completely cover and protect the needle208. At this stage, the actuator assembly will have advanced forwardly relative to the housing to the point where the latches50snap into engagement with the rear sockets126on the arms38. With the latches so re-engaged, the actuator assembly is locked in a position in which the needle shield cannot be urged back into the housing. In this configuration, the rear portion of the shield on which a label bearing the biohazard icon will be exposed, indicating that the device has been used and that it contains a biohazard sharp.

From the foregoing, it will be appreciated that the various aspects and features disclosed may be used in varying combinations, depending on the specifics of the intended application, the medication and the circumstances in which it can be expected to be injected. Among the features described are an auto-injector having a flat housing; an auto-injector having a broad flat surface with easily understood pictograms of sufficient size to enhance immediate understanding of the manner of use of the device; an auto-injector for rapid bolus delivery having a flat housing dimensioned to be less bulky and easily carried on one's person; a needle shield for an auto-injector that is of a generally flat configuration to present a broad face adapted to carry a label with indicia evident of a biohazard; an auto-injector with a housing having elastomeric grips embedded with a material to cause the grips to glow in a darkened environment; an auto-injector in which the injection needle and actuation member are located at the same end of the housing of the device and where the actuator also serves as a needle guide and a needle shield; an auto-injector in which the needle is concealed at all times, including before, during or after use; an inherently safe three step method for using an auto-injector that includes breaking a seal, removing a cover and applying the injector to the injection site; as well as all other features described in this specification.