Abstract:
An injection device comprising an outer housing adapted to receive a syringe for holding a volume of a medicament, said syringe comprising a barrel, a needle at one end of the barrel, and a plunger, axially moveable within the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing. The injection device further comprises an inner housing intermediate the outer housing and at least part of the barrel and/or plunger, an energy source in communication with the inner housing, and blocking means capable of preventing said inner housing moving axially under the influence of said energy source. The device is moveable between two positions, namely a first position in which the inner housing is prevented from moving axially forward by engagement with said blocking means; and a second position in which the inner housing is disengaged from said blocking means and is capable of acting on the syringe under the influence of said energy source to move said at least part of the needle out of said outer housing. The device is moveable from said first position to said second position by movement of said outer housing relative to said inner housing and actuation of a trigger.

Description:
[0001]    This invention relates to injection devices and more specifically to autoinjector devices for the administration of liquid medication, for example, insulin or growth hormone. 
       BACKGROUND 
       [0002]    Many types of autoinjector devices exist for providing an automatic means for delivering a dose of medicament. An example of a known autoinjector device is described in the applicant&#39;s granted European Patent EP-B-1715903 (The Medical House plc). 
         [0003]    Many autoinjectors described in the prior art comprise an energy source such as a spring or compressed gas that is actuated by a user to drive the needle into the injection site and deliver a dose of medicament. For example, in EP-B-1715903, the delivery of medicament is actuated by sliding an outer housing relative to other components of the device towards the injection site. In other devices, a button is pressed to release stored energy and initiate delivery of the medicament. 
         [0004]    In UK patent GB-B-2239180 (Glaxo Group Limited), a self-injecting device is described that has a trigger, a release mechanism and separate means, controlled by the release mechanism, to discharge medicament. The device has a body formed from two parts that are moveable with respect to one another. The discharge means are actuated by operation of the trigger and release mechanism, and movement of one part of the body relative to the other part. 
         [0005]    The actuation means in prior art autoinjectors varies between devices and the choice of actuation means is usually based on technical considerations such as ease of operation. However, it is found that actuation means that are easy to operate are susceptible to accidental delivery of medicament which may be dangerous. To overcome this problem, some autoinjector devices incorporate safety catches or locks that prevent accidental actuation. In these devices, the safety catch must be disengaged before the device can be actuated using the usual actuation means. The disengaging of a safety catch or similar mechanism adds an extra step to the actuation process. The extra step may be complicated and unintuitive and may not allow for a sufficiently quick delivery of a dose of medicament in an emergency situation where the user may be panicked and/or suffering. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0006]    In accordance with the present invention there is provided an injection device comprising an outer housing adapted to receive: 
         [0000]    a syringe for holding a volume of a medicament, said syringe comprising a barrel, a needle at one end of the barrel, and a plunger, axially moveable within the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing; 
         [0007]    the injection device further comprising: 
         [0008]    an inner housing intermediate the outer housing and at least part of the barrel and/or plunger; 
         [0009]    an energy source in communication with the inner housing; and 
         [0010]    blocking means capable of preventing said inner housing moving axially under the influence of said energy source; 
         [0011]    the device being moveable between two positions, namely 
         [0012]    a first position in which the inner housing is prevented from moving axially forward by engagement with said blocking means; and 
         [0013]    a second position in which the inner housing is disengaged from said blocking means and is capable of acting on the syringe under the influence of said energy source to move said at least part of the needle out of said outer housing;
       wherein said device is moveable from said first position to said second position by movement of said outer housing relative to said inner housing and actuation of a trigger.       
 
         [0015]    The user must then perform two actions, namely move the outer housing relative to the inner housing and actuate the trigger to move the device from the first position to second position. A result of this is that the risk of accidental firing is reduced. 
         [0016]    Preferably, the inner housing is biased axially forward by said energy source in said first position so that upon disengagement of the inner housing from the blocking means, the inner housing is immediately urged axially forward under the influence of the energy source. In one particularly preferable embodiment, the energy source is a spring. In an alternative preferable embodiment, the energy source is compressed gas. 
         [0017]    The device preferably further comprises a spring housing intermediate said outer housing and said inner housing that may serve as a surface for the energy source to act against. 
         [0018]    In one particularly preferable embodiment, the blocking means prevent said inner housing moving axially forward under the influence of said energy source by blocking the axial path of at least part of said inner housing. In this embodiment, the inner housing is prevented from forward axial movement by axially abutting the blocking means. 
         [0019]    In an alternative preferable embodiment, the blocking means comprises a radially moveable component that can be radially urged against a surface of said inner housing so that friction prevents said inner housing moving axially forward under the influence of said energy source. In this alternative embodiment, the inner housing is axially restrained through friction and not axial abutment. In a further alternative embodiment, the inner housing may be axially restrained by a combination of friction and abutment. In any embodiment, the blocking means prevent the inner housing from moving axially forward under the influence of the energy source. 
         [0020]    Preferably, the trigger comprises a disengagement element and, upon actuation of the trigger, said disengagement element is capable of disengaging said inner housing from said blocking means to allow said device to move into said second position. In the case where the inner housing is axially restrained through axial abutment with the blocking means, the disengagement element preferably comprises axially extending ribs. Preferably the ribs are axially moveable with respect to said inner housing and are adapted to disengage said inner housing from said blocking means upon axially moving relative to said inner housing. 
         [0021]    Further preferably, the ribs disengage said inner housing from said blocking means upon axially moving relative to said inner housing by a disengagement distance; and 
         [0022]    in said first position, said ribs are axially moveable relative to said outer housing by a first distance and said outer housing is axially moveable relative to said inner housing by a second distance; 
         [0023]    where said first distance plus said second distance is greater than or equal to said disengagement distance. In the first position, axial movement of said ribs is preferably limited relative to said outer housing to not exceed said first distance, and axial movement of said outer housing is preferably limited relative to said inner housing to not exceed said second distance. Preferably, the axial movement of said ribs is limited relative to said outer housing and axial movement of said outer housing is limited relative to said inner housing by at least one catch on said outer housing; 
         [0024]    where each of said at least one catch has an axially extending portion that abuts said spring housing or a component fixed axially thereto to limit relative displacement between said outer housing and said inner housing, and a radially extending portion that is in axial alignment with at least a portion of said trigger to limit relative displacement between said ribs and said outer housing. In these preferable embodiments, the individual action of moving the outer housing relative to the inner housing or moving the ribs relative to the outer housing are insufficient to cause the ribs to disengage the inner housing from the blocking means. The user must therefore perform two distinctly different actions to deliver a dose of medicament. 
         [0025]    In a particularly preferable embodiment, the trigger means comprises a button and said trigger means is actuated by depressing said button. In this embodiment, the exterior of the device will resemble some button-actuated prior art autoinjector devices whilst the inner mechanism may be distinctly different. Preferably, the button is connected to said ribs and depression of said button proportionally moves said ribs axially forward relative to said outer housing. In one embodiment, the user must depress the button by an amount equal to the first distance to move the ribs relative to the outer housing by the first distance. Further preferably the inner housing comprises a plurality of radially flexible tags, and said blocking means comprises apertures in said spring housing for receiving said flexible tags and preventing forward axial movement of said inner housing in said first position. The ribs are preferably adapted to contact said flexible tags and cause said tags to flex radially inwards, out of said apertures, to disengage said inner housing from said blocking means. 
         [0026]    When the device is in the second position with the inner housing disengaged from the blocking means, the inner housing preferably acts on the barrel of said syringe to move said at least part of the needle out of said outer housing so that the needle may penetrate an injection site. From said second position, the device is preferably moveable into a third position in which the inner housing acts on the plunger but not the barrel such that, in use, said plunger is moveable axially into said barrel so as to expel medicament through the needle and a dose of medicament may be delivered to the injection site. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: 
           [0028]      FIG. 1  is a sectional view of part of an autoinjector device according to the present invention and  FIG. 1A  shows a detailed view of the rear of the device (with a transparent outer housing for clarity); 
           [0029]      FIG. 2  is a sectional view of the autoinjector device of  FIG. 1  with the button depressed; 
           [0030]      FIG. 3  is a sectional view of the autoinjector device of  FIG. 1  with the outer housing moved axially forward; and 
           [0031]      FIG. 4  is a sectional view of the autoinjector device of  FIG. 1  with the outer housing moved axially forward and the button depressed. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 1  shows a sectional view of an exemplary embodiment of an autoinjector device  10  according to present invention. The device  10  has a housing including an outer housing  12  which houses a syringe  14 . The syringe  14  is adapted to hold a volume of medicament and comprises a barrel  16 , a needle (not shown) at one end of the barrel  16 , and a plunger  18 , axially moveable within the barrel  16 . The needle is axially moveable in and out of a front end of the device&#39;s housing but is biased to be normally wholly inside the housing. 
         [0033]    The device further comprises an inner housing  20  disposed intermediate the outer housing  12  and at least part of the syringe  14 . Prior to actuation for delivery of medicament, at least a part of the inner housing  20  is disposed axially rearward of the barrel  16  of the syringe  14 . The device  10  further comprises a spring housing  22  intermediate a portion of the inner housing  20  and the outer housing  12 . A spring  24  is located between the spring housing  24  and the inner housing  20  and biases the inner housing  20  axially forward. In alternative embodiments, other energy sources, such as compressed gas, may be used in place of the spring  24 . In the embodiment shown in the Figures, the inner housing  20  has a plurality of radially flexible tags  20 A that, in a relaxed position, are disposed in apertures  22 A of the spring housing  22 . With the tags  20 A located in apertures  22 A, the axial path of the inner housing  20  is blocked by the spring housing  22  and the inner housing  20  is prevented from moving axially forward under the influence of spring  24 . 
         [0034]    The inner housing  20  is adapted to act on the syringe  14  under the influence of the spring  24  to move at least part of the needle out of the outer housing  12  and then act on the plunger  18  to expel medicament through the needle. These steps are prevented from taking place, however, when the tags  20 A of the inner housing  20  are located in the apertures  22 A of the spring housing  22 . 
         [0035]    In order to deliver a dose of medicament, therefore, the user must dislodge the tags  20 A from the apertures  22 A. To facilitate this, the device is provided with a trigger. In the embodiment shown in the Figures, the trigger comprises a button  26  having a finger pad  27  and axially extending ribs  28 . The ribs  28  extend axially forward from the rear of the device  10  in between the inner housing  20  and the outer housing  12  and are axially aligned with the tags  20 A (in their relaxed state) of the inner housing  20 . The finger pad  27  protrudes through an opening  12 A at a rear end  12 B of the outer housing  12  allowing access by the user. The button  26  is biased axially rearward from the spring housing  22  by a spring  30 , although other biasing means may be envisaged. 
         [0036]    When a front cap (not shown) of the device  10  is removed, the outer housing  12  can be moved axially forward with respect to the spring housing  28  and inner housing  20 . The extent of the possible axial displacement of the outer housing  12  relative the spring housing  22  and inner housing  20  is determined by catches  13  (see  FIG. 1A ) that extend axially forward from the rear end  12 B of outer housing  12 . The catches  13  each have an axially extending portion  13 B and a radially extending portion  13 A. When the outer housing  12  is moved axially forward relative to the spring housing  22  and inner housing  20  by a distance y, the axially extending portions  13 B of catches  13  abut the spring housing  22  and further axial displacement of the outer housing  12  is prevented. 
         [0037]    The button  26  is axially displaceable relative to the outer housing  12 . However the extent of relative displacement is also determined by the catches  13 . When the button  26  is moved axially forward relative to the outer housing  12  by a distance x, the finger pad  27  abuts radially extending portions  13 A of the catches  13  and further axial displacement of the button  26  is prevented. 
         [0038]    The button  26  can therefore move axially forward by a total distance x+y relative to the spring housing  28  and inner housing  20  when the outer housing  12  is moved axially forward and the button  26  is depressed by the user. In the particular embodiment shown in the Figures, either action can be done before the other to displace the button  26  by a total distance of x+y relative the spring housing  22  and inner housing  20 . 
         [0039]      FIG. 2  shows the device with the button  26  depressed and the outer housing  12  in its original, undisplaced position. In this condition, the ribs  28  have moved a distance x axially forward relative to the inner housing  12  (compared with the device shown in  FIG. 1 ). The displaced ribs  28  may engage with the tags  20 A of the inner housing  20 , but the displacement x of the ribs  28  is insufficient to unlatch the tags  20 A from the apertures  22 A. 
         [0040]      FIG. 3  shows the device  10  with the outer housing  12  displaced axially by a distance y with respect to the inner housing  20  and spring housing  22 . In this position, the button  26 , and therefore the ribs  28 , are displaced axially a distance y with respect to the inner housing  20  and spring housing  22 . The displaced ribs  28  may engage with the tags  20 A of the inner housing  20  but do not unlatch the tags  20 A from the apertures  22 A. As shown in  FIGS. 2 and 3 , the individual actions of displacing the outer housing  12  and depressing the button  26  are, each in themselves, insufficient to unlatch the radially flexible tags  20 A from apertures  22 A and actuate the device  10 . This is because the ribs  28  must be displaced by a disengagement distance that is greater than the greater of x or y, individually, for actuation to take place. Because of the arrangement of catches  13 , the ribs  28  are only permitted to be displaced by the disengagement distance relative the inner housing  20  and spring housing  22  if the button  26  is depressed by a distance x relative the outer housing  12  and the outer housing  12  is moved axially forward by a distance y relative the inner housing  12  to the position shown in  FIG. 4 . The disengagement distance is less than or equal to the sum x+y. In  FIG. 4 , the button  26 , and therefore the ribs  28 , are displaced by a distance x+y relative to the inner housing  12  as compared to the device of  FIG. 1 . 
         [0041]    When displaced by the disengagement distance, the ribs  28  may engage with the tags  20 A and cause them to flex radially inward, out of engagement with apertures  22 A ( FIG. 4  does not show the tags  20 A flexed radially inwards but illustrates the extent of interference between the ribs  28  and tags  20 A). When the tags  20 A are flexed radially inwards, the spring housing  22  is no longer axially aligned with them and so the inner housing  20  is free to move axially forwards under the influence of the spring  24  to expose the needle and deliver a dose of medicament. 
         [0042]    In a particularly preferable embodiment, the inwardly flexed tags  20 A drive the barrel  16  axially forward to move at least a part of the needle out of the outer housing  12 . When the needle extends out of the outer housing by the desired amount, the tags  20 A are radially aligned with further apertures that allow them to relax once more, moving radially outward. Preferably at the same time, during needle insertion, a set of rear tags  20 B are urged radially inwards into axial alignment with the plunger  18  of the syringe  14 . Under the influence of the spring  24 , the rear tags  20 B move the plunger  18  axially forward with respect to the barrel  18  expelling medicament out of the needle. When a dose of medicament has been delivered, both of sets of tags  20 A,  20 B are in a relaxed state out of the axial path of the barrel  16  and the needle so that the syringe  14  is free to retract under the influence of a return spring (not shown). 
         [0043]    The skilled reader will appreciate that alternative delivery processes are compatible with the actuation mechanism of the present invention and that the above described process represents one of many possible examples. In all embodiments, the device is actuated by the user moving the outer housing  12  relative to the inner housing  20  and actuating a trigger. The button  26  described above is a particularly preferable embodiment of the trigger. However the invention is not limited to button actuation. In alternative embodiments, for example, the trigger may be a slider located on the outer housing  12 . In any case, the inner housing is prevented from moving axially forward due to engagement with blocking means or gripping means. 
         [0044]    The blocking means may comprise any mechanism that is capable of blocking the axial path of at least part of the inner housing and/or radially gripping the inner housing to prevent the inner housing moving axially forward under the influence of the energy source. For example, the blocking means may be apertures with which a radially extending portion of the inner housing can engage thereby preventing axial movement of the inner housing. Alternatively, the blocking means may be radial components that engage with at least a part of the inner housing. For example, this may be a front portion of the inner housing or apertures in the inner housing. 
         [0045]    The blocking means may comprise gripping means in the form of a radially biased component that, for example, is biased radially inwards to grip an outer surface of the inner housing, or is biased radially outwards to grip an inner surface of the inner housing. Frictional forces between the inner housing and the blocking means would then be capable of preventing forward axial movement of the inner housing under the influence of the energy source. 
         [0046]    For example, the blocking means may be apertures  22 A in the spring housing  22  into which tags  20 A of the inner housing  20  can engage thereby blocking the axial path of the tags  20 A and therefore the inner housing  20 . The inner housing  20  is then prevented from moving axially forward under the influence of the energy source due to the engagement between the tags  20 A and apertures  22 A. 
         [0047]    The movement of the outer housing  12  and actuation of the trigger act together (in any order) to disengage the inner housing  20  from the blocking means and allow delivery to take place. This may be achieved by a disengagement element that may be an element of the outer housing, an element of the trigger, or an element of both. In order to disengage the inner housing  20  from the blocking means, the disengagement element may move or cause the movement of the component previously blocking the axial path of the inner housing to a position where it no longer blocks the axial path of the inner housing. In the case where gripping means are employed to prevent axial movement of the inner housing, the disengagement element may disengage the inner housing from the gripping means by removing the bias from the radially biased component so that the friction between the inner housing and the gripping means is insufficient to prevent forward axial movement of the inner housing. Alternatively, the disengagement element may cause the radially biased components to be counter-biased in the opposite radial direction to reduce the friction between the gripping means and inner housing to a level that is insufficient to prevent forward axial movement of the inner housing. 
         [0048]    For example, the disengagement element may be the ends of the ribs  28  which ride against a chamfered surface of tags  20 A to urge the tags  20 A radially inwards and out of engagement with the apertures  22 A. When tags  20 A are out of engagement with apertures  22 A, the axial path of the tags  20 A is clear and the inner housing  20  may move axially forward under the influence of the energy source. 
         [0049]    The individual acts of sliding the outer housing  12  axially forward, or actuating the trigger, are not separately capable of actuating the device to deliver a dose of medicament. The user must therefore perform both steps to give an injection and therefore, the risk of accidental firing is minimised. 
         [0050]    For a given device, the trigger mechanism can be chosen to be one that is suitable for use with a particular drug or is preferred by a particular type of patient. The trigger mechanism on an emergency autoinjector for delivering adrenaline, for example, may be different to the trigger mechanism on a device designed to be used frequently such as an insulin autoinjector for a diabetic patient. Similarly, the trigger mechanism on an autoinjector designed to be used by the patient may be different to the trigger mechanism on an autoinjector designed to be used by a medical practitioner. The skilled reader will appreciate that the trigger may be a button or a slider, or any other interface component that may be actuated by the user to bring about a mechanical effect. 
         [0051]    The present invention allows a familiar, and therefore, perhaps, more user-friendly, actuation means to be applied to an improved autoinjector device. This has the surprising effect of providing a relatively more complicated device (as compared with that described in EP-B-1715903) in order to provide an exterior mechanism that is appears consistent with known autoinjectors with which the user may already be familiar. Familiarity, intuitiveness and ease of use are three very important factors to consider in providing a user with a safe and reliable autoinjector. 
         [0052]    Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. 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. 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. 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. 
         [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.