Filled syringe with breakaway force feature

Abstract

To provide a jet injector that includes a prefilled syringe.SOLUTION: A syringe 18 includes a fluid chamber 22 that contains a medicament. The syringe 18 also has an injection-assisting needle 24, and a plunger 28 is movable within the fluid chamber 22. A housing 12 is configured for allowing insertion of the needle 24 to a penetration depth. The housing 12 includes a retractable guard 66, and an interference component, such as a lock ring, that is adjacent to the retractable guard 66 and interferes with movement of the retractable guard 66. An energy source biases the plunger 28 to produce an injecting pressure to jet-inject the medicament from the fluid chamber 22 through the needle 24 to an injection site.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001]

[0001] This application claims priority to U.S. Provisional Application No. 61 / 607,339, filed March 6, 2012, the disclosure of which is incorporated herein by reference.

[0002] This application relates to jet injectors, and in some embodiments, to needle-assisted jet injectors that use low jet injection pressures and include a locking ring that provides breakaway force resistance. [Background technology]

[0003]

[0003] Some jet injectors are equipped with a needle guard that must be retracted prior to needle insertion and jet injection triggering. Summary of the Invention [Problem to be solved by the invention]

[0004] Triggering a jet injection typically requires some force. To ensure sufficient needle guard movement for needle insertion and triggering, it may be desirable to require a breakaway force before dominant needle guard retraction to ensure that the needle insertion and triggering force is overcome. The present invention addresses this issue. [Means for solving the problem]

[0005]

[0004] In some embodiments, the present invention relates to a jet injector. In one embodiment, the jet injector has a pre-filled syringe with a container portion defining a fluid chamber for containing a medicament, and an injection-assist needle disposed at a distal end of the chamber, the injection-assist needle having an injection tip configured to pierce an insertion location and defining a fluid passageway in fluid communication with the chamber for injecting fluid from the chamber into the injection site, the jet injector further has a plunger movable within the fluid chamber and a housing that houses the pre-filled syringe, the housing configured to allow insertion to an insertion point that is a penetration depth below the surface of the needle at the injection location, the housing configured to prevent the needle from penetrating into the guard. and an injection position where the tip of the needle is exposed for insertion into the insertion point, and the housing includes an interference element adjacent the retractable guard that interferes with movement of the retractable guard when the retraction element moves at least partially from the protection position toward the injection position, the housing also includes a syringe support that supportively mounts a pre-filled syringe within the housing, and the housing also includes an energy source configured to apply a selected force to the plunger to generate an injection pressure on the medicament in the fluid chamber for jet injection of the medicament from the fluid chamber through the needle and into the injection site.

[0006] In some embodiments, the energy source and pre-filled syringe are configured to provide an injection pressure of between about 80 psi and 1000 psi when injecting the medication. In one embodiment, the energy source and pre-filled syringe are configured to provide an injection pressure of less than about 500 psi and greater than about 90 psi when injecting the medication. In other embodiments, the energy source and pre-filled syringe are configured to generate an injection pressure of at least about 100 psi when injecting the medication. In one embodiment, the energy source and pre-filled syringe are configured to provide an injection pressure of up to about 350 psi when injecting the medication.

[0007] In some embodiments, the pre-filled syringe is equipped with an injection-assist needle. and a proximal end opposite the distal end, and a syringe support for axially supporting the proximal end of the prefilled syringe during jet injection of the medication, wherein the distal end of the prefilled syringe is substantially unsupported axially. In one embodiment, the container portion of the prefilled syringe is formed from blown glass, and in another embodiment, the injection-assist needle is glued to the glass.

[0008] In one embodiment, the interference element is a ring having at least one abutment arm extending distally from a proximal end sized to fit within the housing, the abutment arm including at least one tapered portion. In one embodiment, the at least one abutment arm includes an engagement portion axially adjacent the at least one tapered portion configured to provide resistance to movement of the retractable guard as the retractable guard moves at least partially from the protecting position toward the injection position.

[0009] In one embodiment, the energy source comprises a spring. In one embodiment, the jet injector further includes an arm biased against the plunger by the spring to generate the injection pressure, the arm having a bell portion in which the spring seats, the bell portion defining a hollow interior configured to receive a pre-filled syringe when the device is in use, and the spring encloses the pre-filled syringe.

[0010] In some embodiments, the jet injector further includes a trigger mechanism operatively associated with the energy source to activate the energy source to jet inject the medicament, the trigger mechanism being configured to activate the energy source after the retractable guard is retracted from the protective position. In one embodiment, the retractable guard is operatively associated with the trigger mechanism to activate the energy source when the guard is retracted to the injection position.

[0011] In some embodiments, the interference element is a sleeve including an engagement portion extending outwardly from an outer surface of the sleeve that is configured to provide resistance to movement of the retractable guard as the retractable guard moves at least partially from the protecting position toward the injection position. In other embodiments, the interference element is a latch portion coupled to the housing that is configured to provide resistance to movement of the retractable guard as the retractable guard moves at least partially from the protecting position toward the injection position.

[0012]

[0011] In some embodiments, the housing is configured to allow the needle to be inserted to a penetration depth that is between about 0.5 mm and about 5 mm below the surface of the insertion location.

[0013]

[0012] In some embodiments, the housing is configured to allow the needle to be inserted to a penetration depth that is between about 11 mm and about 13 mm below the surface of the insertion location.

[0014] In some embodiments, the chamber contains about 0.02 mL to about 5 mL of drug. Accommodates.

[0015] In some embodiments, the penetration depth and injection pressure are adjusted to the Enough to substantially prevent backflow.

[0016] In another embodiment, the jet injector further comprises a pre-filled syringe. The syringe support includes a syringe cushion associated with the syringe support and the pre-filled syringe to compensate for irregularities in the shape of the syringe.

[0017] In some embodiments, the present invention relates to a locking ring for a jet injector. In other embodiments, the locking ring includes at least one abutment arm extending distally from a proximal end of a body sized to fit within a housing of the jet injector, the abutment arm including at least one tapered portion and at least one engagement portion axially adjacent the at least one tapered portion, the engagement portion configured to provide resistance to movement of a retractable guard of the jet injector, and including at least one flap portion radially adjacent the at least one abutment arm extending distally from the proximal end of the body.

[0018] The foregoing summary of the invention, as well as the following detailed description of embodiments of the invention, will be better understood when read in conjunction with the accompanying drawings of exemplary embodiments, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a side view of one embodiment of a jet injector according to the present invention, showing the injector prior to injection. [Figure 2] 2 is a cross-sectional view of the jet injector of FIG. 1 taken along line II-II. [Figure 3] FIG. 2 is a perspective view of a pre-filled syringe for use with the jet injector of FIG. 1. [Figure 4] FIG. 2 is a perspective view of a syringe cushion of the jet injector of FIG. 1. [Figure 5] FIG. 2 is a cross-sectional view of the jet injector of FIG. 1, showing the injector at the start of the jet injection. [Figure 6] 10 is a graph showing the change in pressure present in a chamber containing a medication over time during a jet injection, according to one embodiment. [Figure 7] FIG. 10 is a side view of another embodiment of a syringe configured to use a narrow diameter pre-filled syringe. [Figure 8] 8 is a cross-sectional view of the syringe of FIG. 7 taken along the plane VIII-VIII. [Figure 9] FIG. 10 is a cross-sectional view of another embodiment of a needle-based syringe for intramuscular jet injection. [Figure 10A] FIG. 10 is a side view of an interference element of a jet injector, according to an exemplary embodiment. [Figure 10B] 1 is a perspective view of an interference element of a jet injector, according to an exemplary implementation. [Figure 11] 10 is a graph illustrating breakaway force over time for a jet injector in accordance with an exemplary embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0020]

[0031] Various embodiments of the present invention are more fully described below with reference to the accompanying drawings. Some, but not all, embodiments of the present invention are shown. The various embodiments of the present invention may be embodied in many different forms and are not limited to the embodiments shown. Like reference numerals refer to similar elements throughout. Unless otherwise expressly stated, the singular terms "a," "an," and "the" include both the singular and the plural.

[0021]

[0032] 1 and 2, an embodiment of a syringe 10 includes a housing 12 configured to allow a user to manipulate the syringe 10. The housing 12 includes an outer housing 14 that substantially houses many of the elements shown in FIG. 2. A syringe support member 16 is housed within and attached to the housing 12. The syringe support member 16 is configured to hold and position a pre-filled syringe 18, which is shown in FIG. 3 . In one embodiment, the syringe support member 16 is substantially secured to the housing 12 by snaps, adhesive, welding, or other known attachment means. The pre-filled syringe 18 includes a container portion 20 defining the interior of a fluid chamber 22, into which a medication to be injected is pre-filled. An injection-assist needle 24 is disposed at the distal end of the pre-filled syringe 18. The needle 24 includes an injection tip 26 configured in a known manner for penetrating a patient's tissue, which in some embodiments is skin. As is known, a needle bore extends through the needle 24. The bore is in fluid communication with the medication in the fluid chamber 22 and opens at the needle tip 26 for injecting the medication.

[0022]

[0033] A plunger 28 is positioned proximally of the fluid chamber 22, opposite the needle 24, to seal the medicament within the fluid chamber 22. In some embodiments, the syringe wall 30 has a tubular portion that, in some embodiments, is closed at a distal end and open at a proximal end to define the fluid chamber 22. The plunger 28 is slidably received within the tubular portion. The pre-filled syringe 18 is configured such that, when the plunger 28 is displaced distally, the volume of the fluid chamber 22 decreases, expelling the medicament from the syringe 18 through the bore of the needle 24.

[0023]

[0034] A needle hub portion 32 is disposed at the distal end of the fluid chamber 22 and has a seal attached thereto. In one embodiment, a syringe flange 34 extends radially from the proximal end of the syringe wall 30.

[0024]

[0035] In one embodiment, the syringe 18 includes a syringe body 36 including a flange 34, a wall 30, and a hub portion 32. In one embodiment, the syringe body 36, including the flange 34, the wall 30, and the hub portion 32, is of unitary construction. A preferred material for the syringe body 36 is glass, although other materials may be used in other embodiments. A suitable pre-filled syringe is the BD Hypak®, which is available in various sizes and volumes and is sold pre-filled with a medication. The glass of the syringe body 36 is glued to the needle 24. Typical medications and categories of medications include epinephrine, atropine, sumatriptan, antibiotics, antidepressants, and anticoagulants. Using a pre-filled syringe 18 facilitates handling of the medication when the injector 10 is assembled, and there is greater knowledge of how the medication will be maintained and acted upon within the pre-filled syringe.

[0025]

[0036] Syringe cushion 38, shown in detail in FIG. 4, in some embodiments is formed from an elastomeric or other resilient material. A flange 40 of syringe cushion 38 extends radially and is positioned and functions as an interface between the distal side of syringe support member 16 and syringe flange 34. A raised portion, such as ridge 42, extends proximally from cushion flange 40 and is configured and dimensioned to abut syringe flange 34.

[0026]

[0037] Prefilled syringes manufactured by the glass-blown process can have significant dimensional tolerances and non-uniformities, particularly in the syringe body 36. The cushion 38 can function to accommodate irregular shapes and also to properly position and locate the prefilled syringe 18 within the syringe support 16. Typically, the axial thickness of the blown glass syringe flange on a 1 mL prefilled syringe is within about ±0.5 mm. BD Hypak® 1 mL standard prefilled syringes have a syringe flange 34 thickness of 2 mm +0.5 or −0.4 mm, while BD Hypak® syringes in the 1 mL long configuration have a flange axial thickness of about 1.65 mm ±0.25 mm. Other variations that occur with typical glass prefilled syringes include: The dimensional variations are the inner diameter and outer shape of the syringe wall 30. These variations can be accommodated by a resilient sleeve portion 44, which extends axially around the inside of the syringe support member 16. In one embodiment, a syringe cushion 38 is received inside the syringe support member 16 and also receives the syringe body 36, in some embodiments, providing a snug fit.

[0027]

[0038] In one embodiment, the sleeve portion 44 includes a radially inwardly extending protrusion 46 that provides a surface area and configuration to allow insertion of a pre-filled syringe 18 during assembly, provide sufficient friction to maintain the syringe in place, and provide cushioning and shock absorption when using the injector 10. An exterior projection 48 is also provided on the sleeve portion 44 that is received within a corresponding recess in the syringe support 16 to prevent axial rotation. If an increased wall thickness of the sleeve portion 44 is not desired, recessed regions 50 can be provided on the interior and exterior of the syringe cushion 38, opposite the corresponding projection 48 on the opposite radial side of the sleeve portion 44. In an alternative embodiment, one or both of the flange 40 and sleeve portion 44 of the syringe cushion 38 are substantially smooth and substantially free of protrusions. In one embodiment, the material and construction of the syringe cushion 38 is sufficient to support the entire pre-filled syringe 18 to withstand a firing force applied axially in a distal direction on the plunger 28. Thus, the entire support for the pre-filled syringe 18 can be provided on the syringe flange 34, while the distal end of the syringe 18 itself is substantially unsupported axially. This helps to withstand shocks on the glass body of the pre-filled syringe 18 created by the increased pressure in the fluid chamber 22.

[0028]

[0039] To radially position the distal end of the pre-filled syringe 18, in some embodiments, the syringe support 16 includes a narrow bore portion 51, which in some embodiments is configured to abut the outside of the syringe wall 30. This is advantageous when the needle 24 is inserted into the patient's skin. The narrow bore portion 51 can be formed from a resilient material, such as an elastomer, and in some embodiments of a plastic material, can be integrally formed with the rest of the syringe support 16.

[0029]

[0040] Referring to FIG. 2 , in one embodiment, a trigger mechanism 52 is housed within the housing 12. The trigger mechanism 52 includes an inner housing 54 that can be attached to the outer housing 14 by snapping, gluing, welding, or other known attachment means. A trigger protrusion 56 extends inward from the proximal end of the inner housing 54 and is resiliently biased outward. The trigger protrusion 56 is received in a recess 58 in a blocking ram 60, preventing axial movement of the ram 60 prior to firing the device. The ram 60 is biased toward the distal end of the syringe 10 by an energy source, which in some embodiments is a compression spring 62, although other suitable energy sources, such as an elastomeric spring or a compression gas spring, can alternatively be used. In one embodiment, the compression spring is a coil spring.

[0030]

[0041] The trigger member of the trigger mechanism 52, such as the latch housing 64, is located within the inner housing. A latch housing 64 is provided on the exterior of the syringe 10 and blocks and retains the trigger projection 56 within the recess 58, preventing premature firing of the syringe 10. The latch housing 64 is slidable within the outer housing 14 relative to the inner housing 54, and in some embodiments, is axially slidable, and in some embodiments, the latch housing 64 surrounds the inner housing 54.

[0031]

[0042] The housing 12 includes a needle guard 66 that is movable relative to the outer housing 14. 1 and 2 in a protective position with the needle 24 positioned within the guard 66. The needle guard 66 is retractable, and in one embodiment, the needle guard 66 is retractable within the outer housing 14 in a proximal direction to an injection position in which the needle tip 26 and the end of the needle 24 are exposed for insertion into a patient, as shown in FIG. 5. In one embodiment, in the injection position, proximal movement of the guard is substantially prevented.

[0032]

[0043] In one embodiment, interference element 134 interferes with movement of the needle guard when the needle guard moves at least partially from the protection position toward the injection position.

[0033]

[0044] In one embodiment, the housing 12 includes an interference element 134, such as a locking ring, adjacent the needle guard 66, which interferes with movement of the needle guard as it moves at least partially from the protective position toward the injection position. The interference element prevents movement of the needle guard until a breakaway force 146 is exceeded. The interference element 134 is shown in FIGS. 10A and 10B. In one embodiment, the interference element 134 is included as part of a ring that includes at least one abutment arm 136 extending distally from a proximal end 138 to fit within the outer housing 14, the abutment arm 136 including at least one tapered portion 140. The abutment arm 136 includes an engagement portion 142 axially adjacent the at least one tapered portion 140 and is configured to provide resistance to movement of the needle guard 66 as it moves at least partially from the protective position toward the injection position. The interference element 134 can include more than one abutment arm 136 and can include more than one corresponding engagement portion 142, with some embodiments including only one abutment arm 136 with an engagement portion 142. The interference element can include at least one flap portion 144 radially adjacent to the at least one abutment arm 136 that extends distally from a proximal end 138 of the interference element 134.

[0034]

[0045] The interference element 134 may be coupled to the housing 12, integrated into a sleeve separate from the housing 12, or include a latch.

[0035]

[0046] Referring to FIG. 11 , a disengagement force 146 is required to overcome the resistance of the needle guard 66 provided by the engagement portion 142 when the needle guard 66 is moved at least partially from the protection position toward the injection position. Referring to FIG. 11 , the disengagement force 146 is the resistance to retraction that acts on the needle guard 66 when the needle guard 66 is initially retracted. The disengagement force 146 is a force that is distinct from the trigger force 148 required to cause a jet injection of medication and is greater than the force provided by the spring 72 that biases the needle guard 66 toward the extended position. The disengagement force 146 is also greater than the force created by the friction of the needle guard 66 sliding over other engagement elements within the device during retraction. In one embodiment, the disengagement force 146 is controlled and is single-use.

[0036]

[0047] 2 , the needle guard 66 is associated with the latch housing 64 such that when the guard 66 is displaced distally, the guard 66 slides the latch housing 64 distally, releasing the trigger protrusion 56 from the recess 58. In one embodiment, the latch housing 64 includes a latch portion 68 that abuts the inner housing 54 such that the latch housing 64 is associated with the guard 66 to bias and maintain the trigger protrusion 56 positioned in a blocking relationship with the ram 60 prior to use (injection) of the device 10. When the latch slides proximally upon retraction of the guard 66 to the injection position, the latch portion 68 slides past the portion of the inner housing 54 that contacts the trigger protrusion 56 to bend it into the recess 58 of the ram 60, allowing the trigger protrusion 56 to move radially outward from the recess 58 and release from the blocking relationship. When this occurs, the spring 62 biases the ram 60 toward the plunger 2. 8 to eject the jet injector 10. In some embodiments, the latch housing 64 defines a trigger opening 70 adjacent the latch portion 68 that is configured to receive a portion of the inner housing 54, such as a surface disposed radially outward from the trigger protrusion 56.

[0037]

[0048] In some embodiments, the guard 66 is resiliently biased distally toward the protective position by a compression coil spring 72. The needle guard 66 also includes an axial opening 74, sized depending on the type of syringe desired, that allows the needle 24 to pass through. This configuration allows the user to press the distal end of the syringe 10 against the patient's skin, pushing the needle 24 into the skin at the insertion point at substantially the same speed as the syringe is pushed. Once the needle 24 is fully inserted to the insertion point and insertion depth, the trigger mechanism 52 initiates a jet injection at the injection point.

[0038]

[0049] Referring to FIG. 5 , in one embodiment, the prefilled syringe 18 and needle 24 are not automatically moved into the patient's skin by the firing energy source during injection. The user preferably gently pushes the entire device to insert the needle 24, and in some embodiments, retracts the guard against the skin in the process. In one embodiment, the prefilled syringe 18 is substantially stationary within the housing 12, and in one embodiment, is substantially fixed to the housing 12. In this manner, the present invention provides gentle handling of the syringe during injection and enables the use of a sufficiently powerful spring 62 or other energy source to generate jet injections without risk of damaging the relatively fragile and complexly shaped prefilled syringe, and also enables the injection of, for example, highly viscous solutions, which in prior art syringes, in which the syringe is moved forward within the housing and inserted into the patient, risk breaking the syringe at a flange or the like. Residual stresses often exist in the glass body of prefilled syringes, and this configuration reduces additional stresses to which the syringe is exposed during use and further protects the syringe. Also, due to the gentle needle insertion possible with this configuration, misalignment of the pre-filled syringe is not operationally significant.

[0039]

[0050] In one embodiment, the injection position of the guard 66 is such that a predetermined length of the end of the needle 24 is exposed from the guard 66. In some embodiments, the opening 74 is of a sufficiently large diameter that when the injection device 10 is compressed, the patient's skin can expand into the opening 74, allowing for the use of a needle that does not protrude beyond the distal end of the guard 66, while still being able to insert the needle to a predetermined depth into the skin. In many embodiments, the distance 76 that the needle tip 26 extends beyond the distal end of the guard 66 will generally approximate the needle insertion depth.

[0040]

[0051] In one embodiment, such as a subcutaneous injection, the guard 66 prevents the needle 24 from being inserted into the skin. The tip 26 is configured to be insertable to a depth of up to about 5 mm below the skin surface. In other embodiments, the insertion depth is less than about 4 mm, and in one embodiment, less than about 3 mm. In one embodiment, the insertion depth is at least about 0.5 mm, and in one embodiment, at least about 1 mm. In other embodiments, the distance the needle extends beyond the guard 66 or the distal surface of the guard 66 that contacts the skin is up to about 5 mm, and in one embodiment, up to about 4 mm, and in other embodiments, up to about 3 mm. In some embodiments, the extension distance 76 is at least about 0.5 mm, and in one embodiment, at least about 1 mm, and in other embodiments, at least about 2 mm. In one embodiment, the tip 26 extends a distance 76 of about 2.5 mm beyond the portion of the guard 66 that contacts the skin at the injection site.

[0041]

[0052] In other embodiments, such as intramuscular injections, the syringe may be inserted such that the needle 24 penetrates the skin to a depth that is less than the penetration depth of the needle 24. The needle guard is configured to be inserted further into the patient, or alternatively, beyond the distal surface of the needle guard. The needle guard is configured to be inserted to a distance of approximately 15 mm. In one embodiment, this distance is between approximately 10 mm and approximately 14 mm. For example, in an embodiment for jet injection of epinephrine, the insertion depth, or the distance extending beyond the guard, is between approximately 11 mm and 17.0 mm, and in other embodiments, between approximately 13 mm and approximately 15 mm. Jet injection with a needle of this length improves delivery of the agent into the patient's tissue compared to non-jet injections. Other exposed needle lengths can be selected for jet injections at different depths below the skin, and in some embodiments, the total insertion length is between approximately 0.5 mm and approximately 20 mm. In some embodiments, the needle guard is configured to retract from a protective position, which in one embodiment covers the entire needle 24 (see FIG. 2), to an injection position in which a desired length of the end of the needle 24 is exposed (see FIG. 5).

[0042]

[0053] In some embodiments, the spring 62 and pre-filled syringe 18 are configured to jet inject the medication. Thus, the spring 62 applies sufficient force to the plunger 28 to increase the pressure in the fluid chamber 22 to a level sufficient to expel the medication as a jet from the needle 24. Jet injection is understood to mean injecting with sufficient speed and force to carry the medication away from the needle tip 26. In manual and auto-injector-type injections, where injection pressures are very low, the medication exits the needle tip within the patient, typically administering a bolus around the needle. In contrast, in the present jet injection device 10, the medication is jet injected distally or otherwise in a generally radial direction by the increased pressure jet, which advantageously improves medication distribution after injection and prevents the formation of large boluses that can leak around the needle and out of the patient, or that can leak out of the needle through a hole after the needle is removed.

[0043]

[0054] Referring to the graph of FIG. 6 , numeral 78 indicates the point in time when firing the device 10, and numeral 80 indicates the point in time when the medicament injection is completed, which in some embodiments indicates when the plunger 28 hits the front wall of the container portion 20. Numeral 82 indicates the initial peak pressure during the injection, and numeral 84 indicates the final low pressure during the injection. In one embodiment, the spring 62 has a linear spring constant, and the injection-assist needle is used to pierce the skin before starting the injection, resulting in a substantially linear drop in pressure from the start of the injection 78 to the completion of the injection. The final pressure 84 at the end of the injection 80 is high enough, even at the end of the firing stroke of the ram 60, that the medicament is jetted and forms very little or no clot around the needle tip 26.

[0044]

[0055] In one embodiment, the peak pressure during injection is less than about 1000 psi, in one embodiment, less than about 500 psi, and in another embodiment, less than about 350 psi. At the end of injection 80, pressure 84 exerted on the medication in fluid chamber 22 is, in one embodiment, at least about 80 psi, in one embodiment, at least about 90 psi, and in another embodiment, at least about 100 psi. In one embodiment of the present invention, the initial pressure 82 is near 330 psi, and the final pressure is about 180 psi; in another embodiment, the initial pressure 82 is about 300 psi, decreasing to near 110 psi at the end of injection 80. The needles used in these embodiments are approximately 26-gauge to 28-gauge, and in some embodiments, near 27-gauge. However, alternative needle gauges can be used if other elements are cooperatively configured to enable the desired injection. For example, in one embodiment for injecting epinephrine, some embodiments of the needle are 20-gauge to 25-gauge, and in other embodiments, 22-gauge. In one embodiment, the components of the syringe 10 are configured to jet inject a medication into a subcutaneous injection site.

[0045]

[0056] The amount of medication contained in and injected from fluid chamber 22 is, in one embodiment, about 0.02 mL to about 4 mL, and in some embodiments, less than about 3 mL. and in other embodiments, on the order of 1 mL. Larger volumes may be selected depending on the particular medication and administration requirements. In one embodiment, a pre-filled syringe pre-filled with the desired amount of medication is assembled into the remainder of the jet injector 10. In one embodiment, the pre-filled syringe contains approximately 1 mL of medication.

[0046]

[0057] In one embodiment, the injection rate is less than about 0.75 mL / sec, and in one embodiment, preferably less than about 0.6 mL / sec, and in one embodiment, at least about 0.2 mL / sec, and in one embodiment, at least about 0.3 mL / sec, and in another embodiment, at least about 0.4 mL / sec. In one embodiment, the entire injection of the agent is completed in less than about 4 seconds, and in one embodiment, less than about 3 seconds, and in another embodiment, less than about 2.5 seconds. In one embodiment, the injection of the agent takes at least about 1 second, and in one embodiment, at least about 1.5 seconds, and in another embodiment, at least about 1.75 seconds. In one embodiment, the injector 10 completes the injection of 1 mL in about 2 seconds at a rate of about 0.5 mL / sec.

[0047]

[0058] U.S. Patent No. 6,391,003 discloses some experimental results of the pressure that can be applied to medication in a glass cartridge using 26-gauge and 27-gauge needles. The table below shows injections of different peak pressures that can be used with pre-filled glass syringes.

[0048] [Table 1]

[0049]

[0060] It is envisioned that higher pressures and flow rates will be used along with shorter needle penetration into the patient's skin to achieve jet injection to a particular desired depth with substantially no drug leakage.

[0050]

[0061] In some embodiments, the jet injection of the device is used to substantially eliminate leakage. It has been found that a short needle can be used to inject medication into different areas of the skin without the need for a needle guard 66. Using a needle 24 extending approximately 2.5 mm from the needle guard 66, a 27-gauge needle 24, a pressure in the fluid chamber 22 with a peak pressure of approximately 300 psi and a terminal pressure of approximately 100 psi, and a flow rate of approximately 0.5 mL / sec, 1 mL of medication was found to be successfully injected with nearly 100% of test injections without leakage. Thus, the needle-assisted jet injector 10 of the present invention reliably enables jet injection of medication using a very short needle, regardless of the patient's skin thickness or the patient's age, weight, and other factors typical of non-jet injections with complex short needles.

[0051]

[0062] 7 and 8 illustrate another embodiment of the present invention, configured to use a pre-filled syringe that is longer and has a smaller diameter than the embodiment of FIG. 2. In the embodiment of FIG. 2, firing spring 62 extends into the bore of pre-filled syringe 18 during the firing stroke, and the narrower pre-filled syringe 88 of syringe 86 does not provide enough space to accommodate the spring. Therefore, ram 90 of syringe 86 includes a bell portion 92, and the bell portion Bell portion 92 defines a hollow interior 94 configured to receive the proximal end of pre-filled syringe 88 and syringe support 96 when injector 86 is in use. Similarly, a bell receiving space 98 is defined around the exterior of pre-filled syringe 88 and syringe support 96 to receive bell portion 92 during firing. Bell portion 92 includes a radially outwardly extending spring seat 100 configured and arranged to seat spring 102. When the trigger mechanism is actuated to fire device 86, spring 102 acts against seat 100, pushing ram 90 against plunger 104 and jetting medicament from fluid chamber 106. As a result, after firing, spring 102 radially surrounds pre-filled syringe 88. Outer housing 108 is wider than outer housing 14 of injector 10 to accommodate bell portion 92 and the larger diameter spring 102.

[0052]

[0063] An available long syringe configuration with a 1 mL capacity has a cylindrical syringe body portion with a diameter of 8.15 mm, which in some embodiments is used in the syringes of Figures 7 and 8, while an available short syringe configuration with the same capacity has a cylindrical syringe body portion with a diameter of 10.85 mm, which in some embodiments is used in the syringes of Figures 1 and 2. Embodiments with a bell portion 92 can be used with wide / narrow syringes, and in some embodiments, the pre-filled syringes have an outer cylindrical wall diameter of less than about 10 mm, and in other embodiments, an outer cylindrical wall diameter of less than about 9 mm.

[0053]

[0064] The syringe 86 also fits around the needle guard 66. The device 86 includes a cap 110 that is associated with the outer housing 108 to prevent retraction of the needle guard 66 and triggering of the device 86. Additionally, the cap 110 seals the needle tip 26 and can be removed prior to use of the device 86. In one embodiment, the cap 110 is configured to fit over the needle guard 66 in a snap-fit ​​manner, accomplished by including a narrow diameter portion 112 that is associated with an enlarged diameter portion 114 of the needle guard 66.

[0054]

[0065] Additionally, the syringe 86 employs a syringe cushion cap 116 that extends from the syringe cushion 118 around the outside of the syringe flange 34 to help capture and retain the pre-filled syringe 88. In one embodiment, a cushion cap 122 is connected to the cushion 118, and in some embodiments, is of integral construction therewith. The cushion cap 122 abuts the distal end of the syringe body 120 to radially position and retain the proximal end of the body 120 when the needle 24 is inserted into the patient. As with the embodiment of FIG. 2, the syringe support 96 is associated with the housing in a substantially fixed position, such as by a mounting portion 124 that captures a protrusion 126 on the syringe support 96.

[0055]

[0066] Referring to FIG. 9, syringe 128 includes a needle guard 130 and is configured to retract further into the syringe housing before trigger mechanism 52 fires the jet injection than the syringes of FIGS. 1, 2, and 5. The syringe in this figure shows the syringe about to fire with trigger mechanism 52 released. The distance 76 that the needle extends beyond guard 130, or beyond the skin-contacting distal surface of guard 130, is about 12.5 mm to about 13 mm in some embodiments. In one embodiment, preferably after the device has been fired and removed from the patient, the guard is configured to re-extend to its protective position, such as by bias spring 72, and is locked in that position by locking member 132 to prevent reuse of the syringe, as is known in the art.

[0056]

[0067] In other embodiments, the guard length, placement of the guard injection position relative to the needle tip ( The length of the needle from the syringe body (including the travel of the guard between the protection position and the injection position) and the length of the needle from the syringe body can be selected to allow for shallower or deeper insertion before the device is fired, providing a smaller or larger distance 76, respectively. In one embodiment, the guard is prevented from sliding back substantially from the fired position for better control of insertion depth into the patient.

[0057]

[0068] All references are hereby incorporated by reference in their entirety. U.S. Patent Application No. 2001 / 0144594, U.S. Patent Nos. 8,021,335, and 6,391,003 are hereby incorporated by reference as if fully set forth herein.

[0058]

[0069] While illustrative embodiments of the present invention are disclosed herein, it should be understood that numerous modifications and other embodiments will be apparent to those skilled in the art. For example, features of various embodiments can be used in other embodiments; for example, the needle and guard cap of Figures 7 and 8 are applicable to the embodiment of Figure 1. It is therefore intended that the appended claims cover all such modifications and embodiments that come within the spirit and scope of the present invention.

Claims

1. 1. An injection device comprising: A pre-filled syringe is provided, the pre-filled syringe comprising: a container portion defining a fluid chamber for containing a medicament; a needle configured to eject the medication from the fluid chamber into an injection site; a plunger movable within the fluid chamber; the injection device further comprises a housing that accommodates the pre-filled syringe, the housing configured to allow insertion of the needle to an insertion point that is an insertion depth below a surface; the housing has a retractable guard movable between a protective position in which the needle is disposed within the guard and an injection position in which a tip of the needle is exposed for insertion into an insertion point; the injection device includes: a biasing element configured to bias the retractable guard toward the protective position; an energy source configured to bias the plunger with a force selected to generate an injection pressure on a drug in the fluid chamber to inject the drug from the fluid chamber through the needle and into the injection site; a trigger mechanism operatively associated with the energy source to activate the energy source to inject the medicament, the trigger mechanism configured to activate the energy source after the retractable guard is moved from the protective position; the injection device further comprises an interference element adjacent the retractable guard, the interference element being a latch with at least one abutment arm, the abutment arm comprising at least one tapered portion and an engagement portion axially adjacent the at least one tapered portion, the engagement portion having a surface angled relative to a slope of the tapered portion, the angled surface of the engagement portion extending radially outward relative to the longitudinal axis from a proximal end of the tapered portion, the engagement portion configured to provide resistance to movement of the retractable guard when the retractable guard moves at least partially from the protection position toward the injection position; a trigger force being the force required to actuate the trigger mechanism and the energy source to eject the agent; a withdrawal force is configured to be applied to the retractable guard to overcome resistance by the engaging portion of the interference element to movement of the retractable guard from the protecting position to the injection position; the release force is a force distinct from the trigger force and greater than the force applied by the biasing element biasing the retractable guard to the protective position; the interference element further includes a flap portion circumferentially adjacent the abutment arm extending distally from the proximal end of the interference element; injection device.

2. 10. The injection device of claim 1, the trigger force is applied to the injection device to cause injection of fluid from the fluid chamber into the injection site; injection device.

3. 10. The injection device of claim 1, the separation force is greater than the frictional force from friction between the retractable guard and the injection device when the retractable guard moves from the protection position to the injection position. injection device.

4. 10. The injection device of claim 1, the withdrawal force is applied during initial movement of the retractable guard toward the injection position; injection device.

5. 10. The injection device of claim 1, the withdrawal force is applied before the trigger force is applied to the injection device. injection device.

6. 10. The injection device of claim 1, further comprising: a syringe support for supportively mounting the pre-filled syringe within the housing; injection device.

7. 7. The injection device of claim 6, the pre-filled syringe having a distal end at which an injection-assist needle is disposed, and a proximal end opposite the distal end; the syringe support axially supports the proximal end of the pre-filled syringe during injection of the medication, and the distal end of the pre-filled syringe is substantially unsupported axially; injection device.

8. 10. The injection device of claim 1, wherein the energy source comprises a spring. injection device.

9. 10. The injection device of claim 1, further comprising: the separation force is the resistance to retraction acting on the guard when initially causing retraction of the guard; the trigger mechanism is configured to activate the energy source after the separation force is overcome. injection device.

10. 10. An injection device according to claim 9, the guard is operatively associated with the trigger mechanism such that the trigger mechanism activates the energy source after the separation force is overcome. injection device.

11. 10. The injection device of claim 1, The insertion depth and injection pressure prevent backflow of the injected medication. injection device.

12. 10. The injection device of claim 1, the separation force acts on the guard when causing an initial retraction of the guard; injection device.

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