Abstract:
A pre-filled, single-use injection device includes a passive dual shield on the patient end of the needle. The device is self-contained so that the entire needle is shielded after use without a separate passive shield system for the non-patient end.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is in the field of injection devices for delivering medications, and specifically to a pre-filled single-use device which protects the user or health care provider from accidental needle-stick. 
     2. Description of the Related Art 
     The prior art teaches various safety shield systems adapted for use with a medication pen. Examples of passive shielding systems include those disclosed in U.S. Patent Application Publication Nos. 2011/0288491 and 2011/0257603, which are incorporated by reference. The needle assemblies disclosed in these publications are adapted to attach to a pen body, and include a proximal or non-patient side needle which extends into the medication compartment of the pen. In addition to shielding the patient-side needle, such shield systems may include a manually or passively activated shield for covering the proximal side needle to prevent accidental needle stick when the shield assembly is removed from the pen body. 
     With the growth of filled pen devices and other formulations approved for self-injection, the demand for single-use injection devices is likely to increase. It is an object of the present invention to apply the teaching of passive shield protection to a disposable, single use injection device having a self-contained construction such that the patient end of the needle is passively shielded before and after use and the non-patient end of the needle is contained within the device to protect the user or health care provider from needle sticks without requiring a passive shield system on the non-patient end. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention is an injection device comprising a hub bearing a needle. The hub has a proximal slot for engaging a thumb button and a distal surface for engaging a shield assembly. The shield assembly comprises an inner shield radially outward of the needle which has features engaging the hub. The shield assembly further comprises an outer shield radially outward of the inner shield which is adapted to retain the inner shield in an initial position and to release the inner shield to a second position covering the needle. The shield assembly also comprises an outer sleeve radially outward of the outer shield. A first spring biases the inner shield in a distal direction covering the needle after use. A small-volume reservoir containing medication is provided in the device adapted to be pierced by the proximal end of the needle cannula to provide fluid connection between the reservoir and the needle cannula. A thumb button having a tab engages the proximal slot on the hub and encloses the reservoir between the thumb button and the hub. The thumb button has a plunger on a proximal side thereof engaging the reservoir to dispense medication from the distal end of the needle. 
     In another aspect, the invention is a method of using the device to administer a single dose of medication by injection and passively contain the distal and proximal ends of the needle after use. The method comprises: providing a single use injection device having a hub bearing a needle, the hub having a proximal slot for engaging a thumb button and a distal surface for engaging a passive shield assembly; a small-volume reservoir containing medication adapted to be pierced by the proximal end of the needle to provide fluid connection between the reservoir and the needle cannula; and a thumb button having a tab engaging the proximal slot on the hub and enclosing the reservoir between the thumb button and the hub, the thumb button having a plunger on a proximal side thereof engaging the reservoir to dispense medication from the distal end of the needle. To administer the injection, the patient or health care professional positions the single use device against the injection site and depresses the thumb button to deliver the single dose by injection. The distal end of the needle is passively shielded after use using any means, including the dual shield embodiment described above using an inner and outer shield arranged around the distal end of the hub and needle. Thus, both ends of the needle cannula are protected, the distal end is passively shielded to prevent accidental needle stick from the distal end of the needle before and after injection and the proximal end of the needle is contained between the thumb button and the hub after use to protect the user against accidental needle stick from the proximal end of the needle. As an additional benefit, the single use device prevents cross-contamination which could be caused by re-use of a pen with a different pen needle. 
     As will be evident to the person of ordinary skill in the art from the following detailed description, variations of the above-described single use device and method of using same may be adapted and practiced without departing from the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a perspective view of the single-use injection device of the invention. 
         FIG. 2  is an exploded view of the device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, the “distal” direction is in the direction of the injection site, and the “proximal direction” is the opposite direction. The “axial” direction is along the longitudinal axis of the injection device. The needle cannula is generally arranged axially in the device. “Radially” is a direction perpendicular to the axial direction. Thus, “radially inward” generally means closer to the needle. “Integral” means one-piece in the state normally encountered by the user—not intended to be taken apart easily. 
     A single use device  100  according to an embodiment of the invention is shown in  FIG. 1  in the state encountered by a user. Needle-bearing hub  10  is completely contained within a shield assembly  20  such that the outer sleeve  28  of the shield assembly  20  itself becomes the body of the device. Only a lip  16  of the hub  10  sits outside the shield assembly, for attachment using an interference fit, heat welding, adhesive, a combination thereof, or other technique known in the art. Similar to existing shield systems, such as the Autoshield DUO™, the shield assembly  20  may comprise an outer shield  26  which covers the needle in an initial state, and an inner shield  24  from which the needle protrudes in the initial state. (Needle  56  is not shown in  FIG. 1 .) The outer shield  26  retains the inner shield  24  in the initial state and moves proximally to release an inner shield  24  from the initial state. A variety of releasable retaining means may be employed to retain and release the inner shield  24 , as described below. Once released, the inner shield  24  is biased by a spring to a second position covering the needle. The inner shield is preferably locked out over the needle in the second, after-use position. Both shields are at least partially encircled by outer sleeve  28 . Wings  22  may be formed on the outer surface of the outer sleeve  28  to provide a finger-hold for the user or health care provider delivering an injection. Generally the inner shield  24 , outer shield  26  and sleeve  28  are made of injection molded plastic, such as polypropylene. Materials and methods of manufacture may be adapted from the medication pen prior art. 
     A more detailed view of the assembly is seen in the exploded view of  FIG. 2 . Rather than adapting the hub  10  for attachment to a pen body, as in the prior art, the hub  10  according to the present invention is adapted for single-use operation by providing a proximal opening  12  on the hub  10  to receive thumb button  30  and a pre-filled, small-volume reservoir  40  containing medication between the thumb button  30  and the hub  10 . According to the preferred embodiments, the opening  12  in the hub is adapted to receive substantially the entirety of the reservoir. 
     The thumb button is guided by tabs  32  that interface with slots  34  on an interior surface of the hub. In embodiments, tabs  32  and axially oriented slots  34  cooperate to cause the thumb button  30  to travel axially, without rotation, when the thumb button is depressed during an injection. In further embodiments, slots  34  on the interior surface of the hub are circumferentially oriented so that the thumb button can be rotated within the proximal opening  12  of the hub. Of course, both axial and circumferential grooves may be provided on the hub to guide the movement of the thumb button in the hub. For example, in one embodiment, the thumb button  30  is prevented from axial movement in a first position, and must be rotated to a position in which tabs  32  engage axially oriented slots for axial movement. Thus, the thumb button may be rotated from a safety position in which injection is not enabled to a position in which injection is enabled. Although the thumb button  30  may move within the hub  10 , the thumb button is not removable by the user during normal use. An advantage of the single-use device is its overall compactness—in embodiments, the length of the device from the proximal end of the thumb button to the distal end of the outer shield may be less than 60 mm, accommodating a standard 4 mm, 5 mm or 8 mm injection depth needle. The single use shielded device may also be used with longer or shorter needles, including intradermal injection depth needles. 
     The interface of the thumb button  30  directly with the hub  10  permits user-friendly adaptation of the single-use injection device. For example, prefilled reservoir  40  may be engaged to the thumb button  30  so that the reservoir  40  rotates with the thumb button within opening  12  in the hub. Slots  34  in the hub may be configured so that rotating the thumb button  30  in the hub  10  allows the reservoir  40  to be moved from a first axial position, in which the proximal end of the needle cannula cannot pierce the septum  44  of the reservoir, to an injection-ready position, in which the septum can be pierced by the thumb button. 
     In another embodiment, the interface of the thumb button  30  and the hub  10  allows the user or health care provider to select from a plurality of dose levels. In this embodiment, a plurality of axially oriented slots provide for longer or shorter axial movement of the thumb button within the hub  10 . Depending on the axial position of the thumb button, plunger  36  on the thumb button  30  engages stopper  42  on the reservoir to a different axial position, ejecting a corresponding dose of medication from the needle  56 . 
     In another embodiment, the thumb button is provided with a locked after-use position. For this purpose, tabs on the thumb button may be provided to mate with corresponding features on the hub in a locking relationship. These corresponding features are adapted to lock at or close to the distal-most position of the thumb button, reached after an injection is administered. In the locked after-use position, the thumb button cannot be removed, and proximal, distal and/or rotational movement of the thumb button is prevented. The exact arrangement, size and number of the corresponding features on the hub and the thumb button for this purpose may be left to the judgment of the person of ordinary skill. Instead of tabs on the thumb button engaging recesses on the hub, tabs on the hub could be made to mate with recesses on the thumb button. Engagement of the corresponding features in a locked after-use position may be accompanied by an audible click to indicate that an injection is complete. 
     The thumb button may comprise a plurality of components. In embodiments, a threaded interface may be provided between the thumb button and the hub so that a component of the thumb button rotates as it is pushed down, similar to some existing medication pens. Typically the rotating component of the thumb button is a separate molded plastic piece located underneath the exterior surface contacted by the user. 
     Single-use reservoir  40  is simpler than a medication pen cartridge because it is adapted to be shipped to the user pre-filled. Thus, the user is not required to install a pen needle on a pen body. However, similar to a medication pen cartridge, the reservoir typically comprises a septum  44 , which is pierced by proximal end of needle  56  during an injection. Stopper  42  seals off the reservoir and can be pushed to pressurize the contents of the reservoir to eject medication from the distal end of needle  56 . However, any medication holder capable of being pierced by the needle and compressed to eject medication may be used in place of the above-described cartridge with septum and stopper without departing from the scope of the invention, including for example a flexible plastic ballast. Usable with any medication that is delivered subcutaneously, the single-use system is advantageously adapted for use with fixed-dose medications, including, without limitation, epinephrine (and other hormone therapies), basal insulin, glucagon-like peptide (GLP-1), leukocyte growth factors, osteoporosis medications such as Forteo®, hormone-based diabetic therapies such as Pramlintide®, and the like. 
     Different mechanisms may be employed to prevent septum  44  from being pierced by the needle  56  prior to injection. In one embodiment, spring  54  is utilized between the needle bearing hub  10  and the pre-filled reservoir  40 . Upon depressing the thumb button  30 , spring  54  compresses and the proximal end of the needle  56  punctures the reservoir septum  44  to create an open fluid path for the medication. Further depressing the button delivers medication to the patient. 
     Other means of preventing the proximal end of needle  56  from piercing the reservoir septum may be adapted for use with the pre-filled device of the invention. For example, a breakable plastic retainer  53  may be used to retain the reservoir in a safety position which is broken by engaging the thumb button  30 . Alternatively, as described above, the reservoir is engaged with the thumb button and is moved axially into a position where the septum can be pierced simply by rotating the thumb button  30 . 
     The disposable device obviates the need for a proximal end shield because the proximal end of the needle is contained within the device when disposed of. The distal end shield system may be adapted from prior art shield systems, including the above-referenced U.S. Patent Application Publication No. 2011/0257603, with few modifications. 
     As an example, according to one preferred embodiment of the invention, the outer shield  26  is pushed into sleeve  28  during an injection, triggering the release of inner shield  24 , and upon withdrawal of the device from the patient&#39;s tissue, the inner shield  24  fully extends through the opening on the distal end of the outer shield into a locked position under bias of the spring  52 . In the after-use position, the inner shield  29  extends beyond the cannula tip, guarding the contaminated tip against accidental needlestick and providing an indication that the device has been used. 
     Automatically releasing the inner shield by proximally moving the outer shield may be accomplished in a variety of ways. To achieve shielding operation according to one preferred embodiment of the invention, outer shield  26  engages grooves on an internal surface of the outer sleeve  28  to prevent rotation of the outer shield relative to the shield assembly during initial proximal movement of the outer shield  26 . Meanwhile, protrusions on the hub nest within lobes formed on the inner shield, to prevent rotation of the inner shield  29  relative to the shield assembly. Further, the inner and outer shields  26 ,  24  are configured with tapered surfaces, arranged so that when the outer shield  26  is telescoped over the inner shield  24  in the initial position, the tapered surfaces abut one another. Proximal movement of the outer shield  26  into the outer sleeve  28 , after the outer shield clears the grooves on the outer sleeve, causes the tapered surfaces to slide against each other to rotate the outer shield  26 . This rotation of the outer shield frees the inner shield to move distally under the bias of spring  52  to a position in which the inner shield  24  covers the needle. The inner shield may engage recesses in the outer sleeve or hub to lock out the inner shield in this after-use state. 
     In this preferred embodiment, outer shield  26  has a distal opening through which the distal end of the inner shield  24  passes when it is biased to the after-use position covering the needle. The outer shield  26  has a tapered shape on the distal end, and a corresponding shoulder portion of the inner shield  24  fits within this tapered portion of the outer shield in the after-use position. 
     Administering an injection with the single-use device according to the invention is substantially the same as administering an injection with a medication pen according to the prior art. The single use device, being smaller, may be more easily manipulated with one hand because of the proximity of the thumb button to the finger holds on the outer sleeve. However, preparing the device for an injection is considerably simplified, because the user is not required to attach a pen needle to a pen body prior to performing the injection or to remove the pen needle after an injection. In the case of a fixed dose embodiment, the user is not required to set the dose. 
     The above described embodiments provide many advantages compared to current medication injection devices and practices using syringes or medication pens and pen needles. Because the needle assembly according to the invention is self-contained, the device provides added convenience compared to the current practices requiring either vial and syringe, or a medication pen and separate pen needle. Further, this concept offers a solution to the risk of cross-contamination between patients in institutional settings compared to pens or syringes because the single-use device locks the cannula from re-use after removal from the patient and provides an indication that the device has been used. Because the device is so much smaller than typical syringes or medication pens and pen needles, it can be disposed of easily after a single use. The above-described embodiments should not be construed as limiting the invention, which is defined in the appended claims.