Abstract:
A safety syringe assembly ( 10 ) adapted for use in an autoinjector comprising a syringe ( 12 ) and a first sleeve ( 22 ) that at least partially surrounds the syringe. The syringe has a barrel ( 14 ) for holding a volume of medicament, a needle ( 18 ) at one end of the barrel, and a plunger ( 20 ), axially moveable within the barrel. The syringe is axially moveable relative to the first sleeve between a first position, in which the needle is exposed, and a second position, in which the needle is surrounded by the first sleeve and is not exposed. The syringe is axially lockable with respect to the first sleeve when in the second position.

Description:
[0001]    This invention relates to a safety syringe, and more specifically to a safety syringe for incorporation into an autoinjector which is capable of shielding the needle after an injection has been delivered. 
       BACKGROUND 
       [0002]    Autoinjectors are well known in the art and provide automatic actuation means for delivering a dose of medicament to a patient. Many autoinjectors are designed around a syringe comprising a needle, barrel and plunger where the user actuates the device by pressing a button, for example, to actuate delivery. Autoinjectors offer an efficient and safe method for delivering an injection which is desirable for both inexperienced and regular users alike. 
         [0003]    For autoinjectors to be economically appealing, it is preferable for them to be reusable and to be capable of using replaceable prefilled syringes. In prior art autoinjectors, to replace the syringe, the user must open the housing of the autoinjector, remove the used syringe and replace it with a new syringe. When removing the used syringe, however, the exposed needle presents a needle-stick injury risk to the user which is undesirable and, under some jurisdictions, unacceptable by law. It is therefore desirable for the needle to be protected and covered as the user removes the used syringe from the autoinjector. 
         [0004]    Generally, the term ‘safety syringe’ is used to describe a syringe device that has means for protecting the user from accidental needle stick injury following the delivery of an injection. Additionally, safety syringes may be designed such that the syringe cannot be re-used. Many prior art safety syringes exist that are operated manually. 
         [0005]    WO-A-2006/127484 describes a manual injection device that comprises a syringe and a needle guard. The needle guard is slidably arranged on the syringe and is biased from a first position wherein the needle is exposed toward a second position wherein the guard covers the needle. After an injection is manually delivered to a patient, the guard is locked in the second position to prevent the needle being exposed thereafter. 
         [0006]    A safety syringe for use with an automatic injection system is described in WO-A-2005/009520. Again, the safety mechanism incorporates a needle shield that is extendable between a retracted position and an extended position that substantially covers the needle. The automatic injection system has a drive system that is configured to depress a plunger, thereby delivering a dose of medicament, and then move the shield to the extended position, upon activation. 
         [0007]    In general, safety syringes are not identical in shape to standard prefilled syringes and include several additional features. Therefore, if a safety syringe is required to be sold as a prefilled unit, then modified filling equipment is needed which may lead to increased production costs. 
         [0008]    It is therefore an object of the present invention to alleviate the above-mentioned disadvantages. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0009]    In accordance with a first aspect of the present invention there is provided a safety syringe assembly adapted for use in an autoinjector comprising
       a syringe having
           a barrel for holding a volume of medicament,   a needle at one end of the barrel, and   a plunger, axially moveable within the barrel; and   
           a first sleeve at least partially surrounding said syringe;   wherein said syringe is axially moveable relative to said first sleeve between a first position, in which said needle is exposed, and a second position, in which said needle is substantially surrounded by said first sleeve and is not exposed; and   said syringe is axially lockable with respect to said first sleeve when in said second position.       
 
         [0017]    Preferably, the safety syringe assembly comprises latching means that are capable of axially restraining said first sleeve relative to said syringe in said first and second positions and wherein, in said first position, said latching means are releasable. 
         [0018]    In a preferred form, the safety syringe assembly includes a second sleeve that has a larger diameter than said first sleeve and is axially fixed relative to said syringe and wherein said latching means form part of said second sleeve. 
         [0019]    According to a second aspect of the present invention there is provided a method of removing a safety syringe assembly from an autoinjector wherein said safety syringe assembly comprises
       a syringe having
           a barrel for holding a volume of medicament,   a needle at one end of the barrel, and   a plunger, axially moveable within the barrel; and   
           a first sleeve that surrounds said syringe and is axially restrained by restraining means within said autoinjector device;   wherein said syringe is axially moveable relative to said first sleeve between a first position, in which said needle is exposed, and a second position, in which said needle is surrounded by said first sleeve and is not exposed; and   said syringe is locked with respect to said first sleeve when in said second position;   said method comprising the steps of   a) opening said autoinjector to provide access to said safety syringe assembly;   b) axially moving said syringe relative to said first sleeve from said first position in which said needle is exposed to said second position in which said syringe is locked with respect to said first sleeve and said needle is not exposed;   c) exerting a rearward axial force to said syringe and removing said syringe and said first sleeve from said autoinjector where said rearward axial force is sufficient to overcome said restraining means.       
 
         [0031]    Further features of the invention are defined in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: 
           [0033]      FIG. 1  is a perspective view of a safety syringe assembly according to the present invention, with the needle shield removed; 
           [0034]      FIG. 2  is a perspective view of the safety syringe assembly of  FIG. 1 , with the needle shield in place, but the outer cylinder removed; and 
           [0035]      FIG. 3  is a cross-sectional view of the outer cylinder. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]      FIG. 1  shows a safety syringe assembly  10  for use in an autoinjector (not shown). The safety syringe assembly  10  comprises a syringe  12 , an inner sleeve  22  and an outer sleeve  24 . In  FIG. 1 , the outer sleeve  24  is shown to be transparent to improve clarity. The syringe has a barrel  14 , a finger flange  16 , a needle  18  and a plunger  20 . The syringe  12  may be a “standard syringe” in accordance with a standard industry specification, or alternatively, the syringe may be any syringe  12  comprising the above mentioned components. 
         [0037]    It is envisaged that the inner sleeve  22  and outer sleeve  24  can be fitted onto a prefilled syringe  12  prior to installing in an autoinjector. During assembly, the syringe  12  is inserted into the inner sleeve  22  so that the needle protrudes from an aperture  30  in a forward end. The inner sleeve  22  is shown more clearly in  FIG. 2  where it can be seen to comprise several axial slots  26  in a front portion  28 . The front portion  28  has a radially protruding annular flange  28   a  that is discontinuous around its circumference due to the slots  26 . The slots  26  lend the front portion  28  a small degree of radial flexibility that allows the syringe  12  to be installed in the inner sleeve  22 . To do this, the front portion  28  must flex radially outwards to allow the needle shield  19  to pass through the aperture  30 . This is because the needle shield  19  has a larger diameter than that of the aperture  30  when the front portion  28  is in a relaxed position. Once the needle shield  19  has passed through the aperture  30 , the front portion  28  can return to its relaxed position and may move into a position intermediate a forward shoulder of the syringe barrel  14  and the needle shield  19 . In the position shown in  FIG. 2 , the syringe  12  is axially restrained from moving forwards by contact between the syringe barrel  14  and the front portion  28  of the inner cylinder  22 . Since a force is required to remove the needle shield  19  from the needle  18 , the syringe  12  is also axially restrained (for forces less than that required to remove the needle shield  19 ) from moving rearward, through contact between the needle shield  19  and the front portion  28  of the inner cylinder  22 . 
         [0038]    As shown in  FIG. 1 , the outer cylinder  24  fits around the inner cylinder  22  and syringe  12 . The outer cylinder  24  has rear clips  32  that clip onto the finger flange  16  of the syringe  12 . The clip connection between the outer cylinder  24  and the syringe  12  is such that they are fixed, both axially and rotationally, with respect to one another. When installed over the inner cylinder  24 , front legs  34  of the outer cylinder  24  clip into front windows  36  of the inner cylinder  22 . The inner cylinder  22  and outer cylinder  24  may be supplied as a sub-assembly, with which the prefilled syringe  12  can be assembled at a later date. Therefore there is no disruption to the conventional syringe filling process; the safety features being fitted as a secondary stage once a sterile prefilled syringe has been created in accordance with the necessary regulations. 
         [0039]      FIG. 3  shows a cross sectional view of the outer cylinder  24  and shows the rear clips  32  and the front legs  34  in detail. As  FIG. 3  shows, the front legs  34  are defined by axial slots  35  in the surface of the outer cylinder  24 . The front legs  34  comprise an axial leg element  34   a  and a radial leg element  34   b  extending radially inwards therefrom. Intermediate the axial leg element  34   a  and the radial leg element  34   b  there is a ramp  34   c , although it should be noted that the ramp does not extend across the entire width of the front legs  34 . The front legs  34  are radially flexible allowing them to flex outwards when being installed onto the inner cylinder  24  and syringe  12 . When installed, the front legs  34  are in a relaxed position with radial leg elements  34   b  disposed in the front windows  36  of the inner cylinder  22 . 
         [0040]    With the inner  22  and outer cylinders  24  installed onto the syringe  12 , the safety syringe assembly  10  can be inserted into an autoinjector. It is envisaged that certain embodiments of the invention will be compatible with the autoinjector described in the applicant&#39;s PCT publication WO-A-2005/070481, however the present invention is not restricted to any one type of autoinjector. Nevertheless, it is preferred that the safety syringe assembly  10  be constrained by constraining means within the autoinjector through some contact between the autoinjector and the inner cylinder  22 . In a preferable embodiment, it is contact between a part of the autoinjector and the annular flange  28   a  of the front portion  28  of the inner cylinder  22  that restrains the safety syringe assembly  10  within the autoinjector device. 
         [0041]    With the safety syringe assembly installed in an autoinjector, the user actuates the autoinjector to deliver an injection. The needle is inserted into an injection site, either by manual or automatic means. Then, a drive mechanism provides a force to the plunger  20  to move it axially forwards within the syringe barrel  14 , expelling medicament through the needle  18 . When the delivery is complete, the plunger will be in a forward position within the syringe barrel  14  and the needle is withdrawn. Again, this may be a manual retraction or may occur automatically. For the autoinjector to deliver another injection, the used syringe  12  must be removed and replaced by another prefilled syringe. The present invention allows the removal and replacement of the entire safety syringe assembly  10 . 
         [0042]    It should be noted that since the claimed invention relates to a safety syringe assembly per se, it is not limited to any particular method or mechanism for drug delivery. The above described method merely serves as an illustrative example of how drug delivery might take place when the claimed apparatus is incorporated in an autoinjector device. 
         [0043]    To remove the used safety syringe assembly  10  from the autoinjector, the user opens the autoinjector and applies a rearward axial force to the finger flange  16  of the syringe  12  and/or the outer cylinder  24 . Since the safety syringe assembly  10  is otherwise axially restrained in the autoinjector, this causes the outer cylinder  24  and syringe  12  to move rearwardly with respect to the inner cylinder  22  and the autoinjector. In doing so, the front legs  34  of the outer cylinder  24  flex radially outwards as ramps  34   c  allow the radial leg elements  34   b  to ride out of the front windows  36 . As the outer cylinder  24  and syringe move collectively rearwardly, the needle  18  is drawn into the inner cylinder  22  and is thereby entirely covered and protected. 
         [0044]    The outer cylinder  24  and syringe  12  continue to move collectively rearwardly with respect to the inner cylinder  22  until the front legs  34  encounter rear windows located at a rear end on the inner cylinder  22 . As shown in  FIG. 1 , the rear windows  38  are in axial alignment with the front windows  36  and front legs  34  and are generally T-shaped, comprising an axial slot  38   a  and a circumferential slot  38   b . When the front legs  34  encounter the rear windows  38 , they flex radially inwards once more to a relaxed position with the radial leg elements  34   b  disposed in the circumferential slots  38   b  and the ramps  34   c  disposed within the axial slots  38   a . Further rearward movement of the syringe  12  and outer cylinder  24  relative to the inner cylinder  22  is prevented by abutment between the radial leg elements  34   b  and the rear edges of circumferential slots  38   b . The ramps  34   c  cannot assist the front legs  34  in riding out of the rear windows  38  since the ramps are disposed within the axial slots  38   a  that are sufficiently long that the ramps  34   c  do not contact the edge. Thus, when the front legs  34  relax radially into the rear windows  38 , the outer cylinder  24  and syringe  12  are locked with respect to the inner cylinder  22 . 
         [0045]    As described above, at this moment, the needle  18  has been completely withdrawn into the inner cylinder  22  so that it is completely surrounded and protected. More importantly, however, the inner cylinder  22  provides a fixed shield around the needle  18  such that the needle is no longer exposed and there is no risk to the user of accidental needle stick injury when removing the safety syringe assembly  10  from the autoinjector. 
         [0046]    As an alternative to the above described embodiment in which removal of the used syringe  12  from the autoinjector causes the needle to be shielded by the inner cylinder  22 , the shielding could instead be deployed during (automatic or manual) retraction of the needle from the injection site after delivery of the medicament. In this latter embodiment, the needle would already be shielded by the inner cylinder  22  before the user opens the autoinjector to remove the used syringe. 
         [0047]    With the needle within the inner cylinder  22 , the safety syringe assembly  10  can be safely removed from the autoinjector. This may be done by operating release means on the autoinjector, or by simply pulling the safety syringe assembly  10  with sufficient force such that the restraining means holding the assembly  10  within the autoinjector are overcome. 
         [0048]    The used safety syringe assembly  10  can then be safely disposed of in the usual way e.g. in a sharps bin. Since the safety syringe assembly  10  only consists of three components (i.e. the syringe  12 , the inner cylinder  22  and the outer cylinder  24 ), each being relatively inexpensive, the assembly can be designed as a disposable unit. The simplicity of the assembly  10  also allows the inner  22  and outer  24  cylinders to be fitted onto prefilled standard syringes. Therefore, no new equipment or modification is necessary to fill the syringes. 
         [0049]    In certain embodiments of the safety syringe assembly, it is preferable for the inner  22  and/or outer  24  cylinders to simultaneously operate as components of the autoinjector. For example, in some autoinjectors, the inner cylinder  22  could also serve as the syringe holder for axially restraining and translating the syringe within the autoinjector. This approach would lead to reduced autoinjector production costs since each autoinjector could be produced with fewer components. 
         [0050]    It is clear from the above description that the present invention offers an effective and efficient apparatus and method for installing and removing a syringe assembly from an autoinjector whilst keeping the needle covered and the user protected. The apparatus comprises few components that may be made from relatively inexpensive materials and is simple in construction. Certain embodiments of the apparatus may also be made specifically for particular autoinjectors and may comprise components that also function as components of the autoinjector. For example, the inner cylinder  22  may comprise part or all of a syringe holder of the type described in our patent application WO 2007/083115. 
         [0051]    Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps. 
         [0052]    Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
         [0053]    Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. 
         [0054]    The reader&#39;s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. 
         [0055]    All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
         [0056]    Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
         [0057]    The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.