The present invention relates to automatic injection devices (“autoinjectors”). In particular, the present invention relates to an autoinjector having an automatically deployable frontal buttress.
Autoinjector mechanisms have commercially been developed to substitute an automated mechanism for the manual action of inserting a hypodermic needle into a recipient's flesh and forcing the liquid medicament out of the syringe, through the hypodermic needle and into the recipient. In some cases, the automated mechanisms are designed to utilize commercially commonplace pre-filled syringes. The pre-filled syringes are typically manufactured by pharmaceutical companies, or in some cases a third party. The manufacturers thereafter assemble the pre-filled syringes into autoinjectors for commercial distribution. Examples of such devices include the EpiPen® manufactured by Meridian Medical Technologies, Inc., of Bristol, Tenn., the Humira® manufactured by Owen Mumford Ltd., of Oxford, United Kingdom, and the SureClick® system marketed by Scandinavian Health Limited, of Florham Park, N.J. Autoinjectors have proven to be beneficial for patients exhibiting psychological paranoia of receiving parenteral injections (e.g., needle phobic individuals and young children) and/or those without the manual dexterity or clear eyesight necessary to self-administer injections using conventional syringes.
Conventional autoinjectors generally provide a compression spring-based mechanism to drive the syringe in the distal direction within a housing (the housing contains the syringe) and some means to initiate the automatic injection process. When triggered, the compressed spring is released from end-to-end confinement. Typically, the spring is confined to abut against an interior surface of the housing about its proximal end such that releasing the compressed spring causes axial extension in the distal direction. The spring, typically acting through one or more surrogate components, impinges upon the syringe, and/or an elastomeric piston element thereof, causing the syringe to translate in the distal direction until the hypodermic needle associated with the syringe extends beyond the distal end of the housing.
The extended length of the needle determines the depth of drug delivery at the injection site. The exposed length of the needle (i.e., that portion of the needle exterior to the autoinjector housing at needle extension) is known as the “needle insertion depth.” The correlation between extended length and insertion depth assumes that the distal end of the autoinjector is pressed against the injection site during autoinjector actuation. In most therapeutic applications, it is important that the depth of needle insertion be accurately controlled so as to assure the drug is delivered into a specific tissue mass, for example the subcutaneous tissue residing between the dermal skin layer and the musculature. Known and repeatable length of needle insertion is therefore a desirable attribute of autoinjector devices.
Billions of pre-filled syringes as described above are manufactured of borosilicate glass on an annual basis. The proximal end of the glass syringe is formed into a radially disposed, disk-shaped flange. The flange is thereafter cut on two sides in parallel planes in close proximity to the syringe body to form oblong and opposing finger grips. This glass syringe configuration is know as a cut-flange configuration. Glass syringes, and more particularly cut flange syringes, represent a number of challenges in autoinjector applications because they are fragile and easily broken components with a relatively high degree of dimensional variability. The high degree of dimensional variability leads to variability in the exposed length of the hypodermic needle beyond the distal end of the glass syringe and the overall length of the syringe. In addition, the cut flanges of such glass syringes have varying degrees of irregularity and asymmetry with respect to a central axis along the center of the syringe barrel and a plane perpendicular to the central axis.
Conventional autoinjectors are configured to stop the syringe at a desired forward position at the end of needle insertion based off of the syringe flange. That is, the syringe flange becomes a de facto point of registration, in other words a datum surface, which dictates the relative axial relationship between the syringe features and the other elements of the autoinjector. Under such configurations, any variability, whether associated with the overall length of the syringe, length of the exposed needle, or variability associated with the flange itself, translates directly into variability in the extended needle length and needle insertion length. In addition, due to the abrupt deceleration of the syringe/carrier assembly at the end of needle insertion, impact loads are imposed on the fragile syringe flanges. In other words, the force applied by the autoinjector in driving the syringe distally creates an opposing force imposed on the flange by its registration point of contact. In addition, a bending moment is borne by the flange as a result of the radial distance between the centerline of the piston and the flange. The bending moment increases the stress applied to the fragile flange increasing the risk of fracture.
Moreover, conventional autoinjectors are typically configured with a fixed stroke length. That is, conventional autoinjectors are designed to drive the plunger of the syringe a fixed distance from some fixed reference point on the autoinjector. Thus, with increased variability in the overall length of the glass syringe used in such autoinjectors, the fixed stroke length results in increased variability of residual medicament volume after injection. Such variability in residual medicament volume translates into significant monetary waste due to the relatively high cost of the drugs used to manufacture the medicaments.
Thus, conventional autoinjectors are deficient in that they cannot accommodate conventional pre-filled glass syringes (i.e., staked-needed syringes) to effectively address the issues associated with fragile and irregular components while assuring accurate needle placement and precise dose delivery due to the dimensional variability of glass syringe manufacturing. As such, there is still a need for an autoinjector that can provide accurate needle insertion depth and precise dose delivery.
In addition, conventional pre-filled glass syringes are typically supplied as an assembly with a needle shield that includes an elastomeric element to provide a means to sealably encapsulate the hypodermic needle.
Such conventional syringes 46 can be used as a stand alone manually operable syringe 46 or in combination with a suitable autoinjector. Such autoinjectors are provided with a means to remove the RNS before administering the injection. This is typically accomplished by a component provided as part of the autoinjector that engages the needle shield during final assembly and provides a graspable handle with which a user can grasp to extract the needle shield in the axial, distal direction. However, the use of such handles to disengage the RNS creates an annular void or open end about the distal end of the autoinjector. Moreover, as the handle to remove the RNS occupies space at the distal end on the autoinjector, this precludes the use of such space for any potential buttress surface upon which the syringe 46 may engage.
Consequently, an autoinjector that is capable of accommodating a glass, cut flange syringe with a RNS attached would present pharmaceutical companies with a significant advantage in being able to provide one primary pre-filled syringe that can be used either in a manual setting or, alternatively, in conjunction with an autoinjector.
In accordance with the present invention, the problems associated with variability and reliability of the needle insertion depth of autoinjectors employing the use of conventional pre-filled glass syringes are solved by registering the stop of the syringe within an autoinjector based upon the front end of the syringe.
In a preferred embodiment, the present invention comprises an autoinjector. The autoinjector includes a housing and a frontal buttress connected to a distal end of the housing. A syringe is housed within the housing and includes a barrel having a shoulder about a distal end of the barrel. An injection assembly is operatively connected to the syringe and configured to bias the syringe from an initial position in which the syringe is shrouded by the housing to an extended position in which a portion of the syringe extends beyond the housing. The frontal buttress is configured to move from a first, open position when the syringe is in the initial position to a second, closed position to engage the shoulder of the syringe when the syringe is in the extended position.
The foregoing summary, as well as the following detailed description of a preferred embodiment of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings an embodiment which is presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
In a preferred embodiment, the present invention provides for an automatic injection device that includes an automatically deployable buttress upon which a syringe can be registered. As shown in
Preferably the injection assembly 12 includes a cap 16, an activation button 18, an inner housing 20, an injection spring 22, a plunger rod 24 having a piston 47, a spring rest 26, a mid housing 28 and an optional syringe ring 30, as best shown in
In an assembled state, the spring rest 26 is releasably connected to about the middle of the plunger rod 24 by cooperating detents. The plunger rod 24 and spring rest 26 are positioned within the inner housing 20 with the injection spring 22 in between and proximal to the inner surface of the inner housing 20 and an outer surface of the spring rest 26. The injection spring 22 is maintained in a compressed state by catches 21 on the inner housing 20 that retain the proximal head of the plunger rod 24. The activation button 18 is positioned on top of the proximal end of the inner housing 20 and the cap 16 and functions to release the catches 21 to release the spring 22 upon depression. The foregoing assembly resides within the mid housing 28 and cap 16.
Referring back to
The syringe guide 36 is housed within the housing 13, is generally cylindrical in shape, and is configured to receive the barrel 51 of a syringe 46. When assembled with the syringe 46, the flange 62 of the syringe 46 rests upon the cushion 34 and the proximal end of the syringe guide 36 (see
The handle 42 (as shown in
The latches 50 (
In an assembled state, as shown in
To activate the injection assembly 12, a user removes the handle 42, and presses the nose 40 against the injection site and depresses activation button 18, thereby causing the plunger rod 24 to disengage from the inner housing 20. Upon disengagement of the plunger rod 24, the injection spring 22, which is initially in the compressed state, expands to exert a driving force on the spring rest 26 that is connected to the plunger rod 24, which subsequently causes the syringe 46 to move distally. In sum, the injection assembly 12 is operatively connected to the syringe 46 and configured to bias the syringe 46 from an initial position (
In the present embodiment, the nose 40 is configured to include the frontal buttress 43. The bases 48 of each of the flexible members 44 are connected to the nose 40 along the interior distal end of the nose 40, as best shown in
In sum, the frontal buttress 43 is configured to move from a first open position (
As shown in
After the handle 42 is removed and upon activation of the autoinjector 10, the injection assembly 12 forces the syringe guide 36/syringe 46 assembly to engage the frontal buttress 43. As shown in
Preferably, the flexible members 44 are also configured with a planar outside surface 58 that is oriented substantially parallel to the centerline (A) when the flexible members 44 are in the closed position, as best shown in
In sum, the present invention advantageously provides for an autoinjector that can accommodate a conventional syringe (such as a pre-filled glass syringe) and provide a robust means to automatically stop forward (i.e., distal) movement and provide a more consistent and accurate frontal position during needle insertion (i.e., needle insertion depth) and dose delivery, respectively, by registering the stop of needle depth insertion upon the shoulder 52 of the syringe 46 rather than the flange 62. By eliminating the load on the syringe flange 62, the risk of syringe flange fracture is also significantly reduced. Moreover, the accuracy of dose delivery and reduction in residual fluid volume within the syringe post-injection is significantly enhanced, thus saving considerable costs associated with manufacturing pre-filled syringes. The present invention also advantageously provides for an autoinjector having an automatically deployable frontal buttress 43 such that the forward end of the syringe 46 becomes the load bearing or datum surface, thereby reducing stress on the syringe flange 62 and reducing variability in needle insertion depth by eliminating the variability associated with overall length and flange dimensions of glass syringes.
In addition, as the present invention is configured for use with conventional pre-filled syringes, such as glass staked-needle syringes, plastic syringes, and cartridge based syringes with needle hubs, there is no need for any additional sterilization of the autoinjector after assembly with the pre-filled syringe as the medicament within the pre-filled syringe is maintained within a sterile environment regardless of the sterility of the autoinjector. This helps reduce the overall costs associated with autoinjector manufacturing. In addition, because of the modular configuration of the present invention, it allows for pre-filled syringes to be assembled and prepared at one location and the autoinjector components to be prepared at a separate location and/or at different times, thus allowing for greater manufacturing versatility. Moreover, as the autoinjector of the present invention can be assembled with conventional pre-filled syringe at the time of use, the two devices are not constrained to a single expiration date of the device. Thus, the usability or shelf life of the autoinjector will not depend upon the expiration date of the pre-filled syringe.
It will be appreciated by those skilled in the art that changes could be made to the embodiment described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiment disclosed, but is intended to cover modifications within the spirit and scope of the present invention as defined by the claims.
This application is a Section 371 of International Application No. PCT/US2009/047483, filed Jun. 16, 2009, which is not yet published, and this application claims the benefit of priority pursuant to 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/074,253, filed Jun. 20, 2008, the disclosure of which is hereby incorporated by reference in its entirety.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2009/047483 | 6/16/2009 | WO | 00 | 9/9/2009 |
Publishing Document | Publishing Date | Country | Kind |
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WO2009/155277 | 12/23/2009 | WO | A |
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