GB2461078A

GB2461078A - Auto injector with sliding outer sleeve

Info

Publication number: GB2461078A
Application number: GB0811313A
Authority: GB
Inventors: Yannick Pierre Louis Hourmand; Rosemary Louise Burnell; Douglas Ivan Jennings
Original assignee: ALICE 123 Ltd
Current assignee: ALICE 123 Ltd
Priority date: 2008-06-19
Filing date: 2008-06-19
Publication date: 2009-12-23
Also published as: GB0811313D0

Abstract

An auto injector for injecting a fluid from a syringe into a human or animal body, the auto injector comprising: a housing 12; a syringe receiving portion 16 for receiving the syringe 6 within the housing 12, the syringe receiving portion 16 being configured such that the syringe 6 is moveable relative to said housing 12 between an injection position at which the needle tip 19 of the syringe 6 is exposed for injection to a retracted position at which the needle tip 19 is shielded by the housing 12; an injection system 10 for carrying out an injection process; and an outer member 4 mounted on said housing 12 so as to be moveable relative thereto between a first position and a second position, the outer member 4 being resiliently biased 24 towards said first position, wherein said outer member 12 is configured to interact with said syringe receiving portion 16 so that, when said syringe 6 is in the injection position, movement of said outer member 4 from said second position towards said first position causes said syringe 6 to move from said injection position to said retracted position.

Description

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AUTO INJECTOR

The present invention relates to an auto injector, in particular to an auto injector where a syringe is automatically withdrawn to avoid injury.

Various arrangements have been proposed for automatically deploying the needle of a syringe and then dispensing its contents, for instance as described in WO 95/35 126, EP-A-O 517 473, US 6,159,181 and WO 03/092771.

During the injection process, the needle needs to be exposed relative to the housing of the auto injector. At other times, for example before and after the injection process, during storage, transport, etc., it is preferable for the needle to be shielded (e.g. enclosed), so as to minimize the risk of injury.

One way of shielding the needle is to provide a removable cap, which may be screwed or snap fastened to the relevant end of the auto injector. When a user wishes to use the auto injector, the cap is temporarily removed. A problem with this approach is that it requires effort from the user to remove and replace the cap. There is also a risk that the user will forget to replace the cap after use. Furthermore, the cap provides no protection against injury in the period between when the cap is removed and when the cap is replaced, although the needle may not protrude from the housing for all of this period.

An alternative approach has been suggested in US 2005/0203466 and US 2005/0101919. Here, a mechanism is provided for causing a protective sheath to extend automatically when the piston of the syringe reaches the end of its travel. The provision of this additional mechanism significantly increases the complexity of the auto injector, leading to higher costs, and makes miniaturization of the device more difficult and expensive. Furthermore, the arrangement provides no protection in the case where the auto injector is removed from the skin prematurely (i.e. before the piston of the syringe has completed its travel), at least for the period between when the auto injector is removed from the skin and the time at which the piston of the syringe has completed its travel and the protective sheath has advanced.

It is an object of the present invention at least to reduce drawbacks with earlier systems and provide an alternative arrangement providing its own advantages.

According to an aspect of the present invention, there is provided an auto injector for injecting a fluid from a syringe into a human or animal body, the auto injector comprising: a housing; a syringe receiving portion for receiving the syringe within the housing, the syringe receiving portion being configured such that the syringe is moveable relative to said housing between an injection position at which the needle tip of the syringe is exposed for injection to a retracted position at which the needle tip is shielded by the housing; an injection system for carrying out an injection process; arid an outer member mounted on said housing so as to be moveable relative thereto between a first position and a second position, the outer member being resiliently biassed towards said first position, wherein said outer member is configured to interact with said syringe receiving portion so that, when said syringe is in the injection position, movement of said outer member from said second position towards said first position causes said syringe to move from said injection position to said retracted position.

A mechanically simple arrangement is thus provided which reduces the risk of injury from the needle of a syringe mounted in an auto injector without requiring a user to manually apply and remove a cap or other shielding device. The device can therefore be manufactured at relatively low cost and in a compact form. Furthermore, improved protection against injury is provided in the case where the injection operation is interrupted before completion because the needle will retract within the housing as soon as the pressure is released on the gripping member. The retraction of the needle is not delayed until the syringe piston has completed its travel.

Optionally, when the syringe is in the retracted position it will not be possible for a user to bring his finger into contact with the needle due to the shielding function of the housing. For example, the needle will be retracted axially (i.e. in a direction parallel to its length or injection direction) so that no part of it extends beyond the part of the housing that will be in contact with the skin during an injection process, the diameter of this part of the housing being preferably substantially less than the diameter of an adult finger.

The outer member is resiliently biassed towards the first position. Optionally, this is achieved by a resilient member such as a spring. Optionally, in use, the first position is axially further away from the injection site than the second position. Optionally, the auto injector is configured so that a user can apply a force to the outer member which is effective to cause the outer member to move against the resilient bias towards the second position by grasping the outer member and pressing the housing of the auto injector against the injection site.

Optionally the outer member will comprise a substantial portion outside of the housing (e.g. where the housing is substantially cylindrical, at a radius larger than an outer radius of the housing), so that it can be easily grasped by a user. The outer surface of the outer member may be provided with a texture to improve grip.

Optionally, the auto injector further comprises an actuator by which a user can cause the injection system to cariy out the injection process. For example, a button, lever, slider or similar may be provided for this purpose. Actuation of the actuator causes both the syringe to advance and pierce the skin of the body to be injected and the piston of the syringe to subsequently push out the fluid within the syringe through the needle. 4..

Optionally, the outer member is configured so that the actuator is more easily accessible by a user when the outer member is in the second position than when the outer member is in the first position. Accidental actuation of the auto injector is therefore made less likely because a user has to actively move the outer member against its bias before the actuator becomes easily accessible. For example, in the case where the gripping member is intended to be moved to the second position by pressing the housing of the auto injector against the injection site, the actuator will only normally become easily accessible when the user is fully ready to carry out the injection process and the auto injector is in the appropriate position.

Optionally, the outer member is configured so that the actuator is substantially inaccessible when in the first position. For example, where the actuator is a button or similar on a lateral side of the auto injector, the outer member may be provided with an opening which lines up and reveals the actuator to a user when the outer member is moved to the second position, but which otherwise covers the actuator and prevents actuation.

Alternatively, the actuator may be located on an end of the auto injector that is axially opposite to the injection direction (i.e. facing away from the injection site in use). In this case, the outer member may be arranged so as to offer an axial opening (an opening in a plane perpendicular to the axis of the syringe) at the end where the actuator is located that is too small to allow access to an adult finger. Such an outer member may be configured so that the actuator is exposed (i.e. extends axially beyond the axial opening of the gripping member) when the gripping member is in the second position, and is protected (e.g. the gripping member extends axially beyond the actuator) when the gripping member is in the first position. This arrangement is simple to construct and ergonomically efficient, in that a user can firmly grip the outer member in the palm of his hand while actuating the actuator rjth his thumb.

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Optionally, the injection system comprises a means for forcing the syringe from the retracted position to the injection position. For example, a resilient device such as a spring may be provided for this purpose. Similarly, the injection system may comprise means for forcing the piston to travel down the bore of the syringe and force fluid out through the needle. Again, a resilient device such as a spring may be used for this purpose. The same resilient device or separate resilient devices may be used for forcing the syringe and pistons to move.

Optionally, the resilient device for biassing the outer member towards the first position applies a larger force (i.e. is stronger) than the resilient device for forcing the syringe from the retracted position to the injection position, and the outer member is configured to interact with the syringe receiving portion such that movement of the syringe from the retracted position towards the injection position cannot occur without a corresponding movement of the outer member from the first position towards the second position. Thus, even if the actuator is inadvertently actuated while the outer member is in the first position, movement of the syringe into the injection position is prevented and the risk of injury further reduced.

Optionally, the auto injector further comprises a disconnection mechanism for disconnecting (from the syringe) the resilient device for forcing the syringe from the retracted position to the injection position, after actuation of the injection process, such that the syringe reaches the injection position, but no force is applied to the syringe thereafter by the resilient device for forcing the syringe from the retracted position to the injection position. Thus, retraction of the needle into the housing is facilitated: the process of retraction does not need to work against the force from the resilient device powering the injection process. Where this disconnection mechanism is present, the outer member can be resiliently biassed towards the first position by a force smaller than can be provided by the resilient device for forcing the syringe from the retracted position to the injection position. As a result of this, the user does not have to exert such a large force to move the outer member from the first position to the second position. This makes the auto injector easier to use. In addition, distortion of the injection surface caused by the pressure of the auto injector against the skin is reduced, which may reduce the risk of injury and/or inefficient injection.

Optionally, a window is provided to indicate to a user how the injection process is progressing. For example, the window may show when the injection process is completed by making a portion of the syringe at the end of the piston's travel visible during use. Alternatively, a window may be provided which allows the quantity of fluid remaining in the syringe to be evaluated from the start of the injection process to the end of the injection process. The window function may be provided by making appropriate portions of the apparatus transparent. These portions may include all or a portion of the outer member, housing, syringe receiving portion and/or other elements which would otherwise interfere with the visibility of the appropriate portion of the syringe.

Optionally, the syringe receiving portion is adapted to receive one or more standard commercially available syringes. For example, the syringe receiving portion may be adapted to receive a "BD HYPAKÂ� SCF" 1 ml long syringe with a 27G x Y2 inch needle, a "Bunder Glas" imi long syringe with a 27G x V2 inch needle, or similar syringes by other manufacturers.

According to an alternative aspect of the invention, there is provided a method of using an auto injector, the auto injector comprising: a housing; a syringe receiving portion containing a syringe within the housing, the syringe receiving portion being configured such that the syringe is moveable relative to said housing between an injection position at which the needle tip of the syringe is exposed for injection to a retracted position at which the needle tip is shielded by the housing; an injection system for carrying out an injection process; and an outer member mounted on said housing so as to be moveable relative thereto between a first position and a second position, the outer member being resiliently biassed towards said first position, the method comprising: when said syringe is in the injection position, releasing said outer member so that said outer member moves from said second position to said first position, said outer member being configured to interact with said syringe receiving portion so that the movement of said outer member from said second position towards said first position causes said syringe to move from said injection position to said retracted position.

The invention will be more clearly understood from the following description, given by way of example only, with reference to the accompanying drawings, in which: Figures 1A to 1C illustrate an un-actuated auto injector according to an embodiment of the invention, with protective cap and shield in place and outer member in first position.

Figure 1A illustrates an axial view of the device.

Figure lB illustrates a cross-sectional view of the device of Figure 1A through perpendicular section Y-Y.

Figure 1C illustrates a cross-section view of the device of Figure 1A through perpendicular section Z-Z.

Figures 2A to 2C illustrate an un-actuated auto injector according to an embodiment of the invention, with protective cap and shield removed and outer member in first position.

Figure 2A illustrates an axial view of the device.

Figure 2B illustrates a cross-sectional view of the device of Figure 2A through perpendicular section Y-Y.

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Figure 2C illustrates a cross-section view of the device of Figure 2A through perpendicular section Z-Z.

Figures 3A to 3C illustrate an un-actuated auto injector according to an embodiment of the invention, with protective cap and shield removed and outer member in second position.

Figure 3A illustrates an axial view of the device.

Figure 3B illustrates a cross-sectional view of the device of Figure 3A through perpendicular section Y-Y.

Figure 3C illustrates a cross-section view of the device of Figure 3A through perpendicular section Z-Z.

Figures 4A to 4C illustrate an auto injector according to an embodiment of the invention after an injection process has been actuated, with outer member in second position and needle in injection position.

Figure 4A illustrates an axial view of the device.

Figure 4B illustrates a cross-sectional view of the device of Figure 4A through perpendicular section Y-Y.

Figure 4C illustrates a cross-section view of the device of Figure 4A through perpendicular section Z-Z.

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Figures 5A to 5C illustrate an auto injector according to an embodiment of the invention after an injection process has been actuated, with outer member in first position and needle in retracted position.

Figure 5A illustrates an axial view of the device.

Figure 5B illustrates a cross-sectional view of the device of Figure 5A through perpendicular section Y-Y.

Figure 5C illustrates a cross-section view of the device of Figure 5A through perpendicular section Z-Z.

Figures 1A to 1C illustrate an auto injector 1 according to an embodiment of the invention. The auto injector 1 comprises a housing 12 within which is mounted a syringe receiving portion 16 having an upper telescopic body 1 6A and a lower telescopic body 16B. The upper telescopic body 16A can be fixedly mounted to the housing 12 by means of a clip (see circled region 28) initially. The clip is implemented by means of engaging portions 1 6C and 1 2B of respectively the syringe receiving portion 16 and the housing 12. The lower telescopic body 1 6B can be retained in place by an outer member 4 (see below); otherwise, it is movable in an axial direction relative to the upper telescopic body 16A and the housing 12.

Mounted within the syringe receiving portion 16 is a syringe 6 having a needle 18 (with needle tip 19), main body 20, and piston 8.

An actuator 10 is provided for initiating an injection process. In the present embodiment, the actuator 10 is a button, which is activated by depressing the button in the axial direction (i.e. in the injection direction, along which the needle of the syringe is pointing). Other actuators, such as sliders, switches, levers, or the like could be used instead of a button without departing from the scope of the invention.

The outer member 4 is provided radially outside of the housing 12. In the present embodiment, the outer member 4 is in the form of a substantially cylindrical or elongate sleeve. However, other shapes or forms which allow a user to grasp the outer member 4 could be used.

The outer member 4 is moveable relative to the housing 12 between a first position and a second position. In the embodiment, movement between the first position and the second position is longitudinal, i.e. parallel to the axis of the syringe 6. When the outer member 4 is in the first position, the actuator 10 is difficult to access or is inaccessible for a user. This is the situation shown in Figures 1A to 1C. A user is prevented from pressing the button of the actuator 10 because the outer member 4 in the first position extends axially beyond the end of the actuator 10 and the opening 22 of the outer member 4 is too small for a fmger to be inserted far enough to access the actuator 10.

The outer member 4 is spring-loaded by a resilient member 24 (e.g. a spring) so as to be biassed relative to the housing 12 towards the first position. This means that in a relaxed state of the auto injector 1, the actuator 10 is difficult or impossible to access for the user. The user needs positively to drive the outer member 4 into the second position in order to access the actuator 10 and initiate an injection process. The likelihood of inadvertent actuation is thereby reduced.

Furthermore, axial movement of the lower telescopic body 1 6B is independently prevented when the outer member 4 is in the first position. This is achieved by provision of engaging portion 4A of the outer member 4, which is configured so that axial movement of the lower telescopic body 16B cannot take place without a corresponding movement of the outer member 4 in the same direction. In the present embodiment, the resilient member 24 is stronger than the resilient device 30 (see below) by which the lower telescopic body I 6B is forced in the injection direction upon actuation. Therefore, even if the actuator 10 is inadvertently actuated while the outer member 4 is in the first position, movement of the syringe 6 in an injection direction will be prevented by the outer member 4 and the risk of injury is reduced.

However, the resilient member 24 may be arranged to be weaker than the resilient device 30 by which the lower telescopic body 16B is forced in the injection direction upon actuation. A weaker resilient member 24 makes it easier for a user to displace the outer member 4 from the first position to the second position, making the auto injector easier to use.

Further shielding of the needle 18, for transport andlor storage, for example, is provided by a cap 2, which may be detachably mounted to the leading end of the auto injector 1. Threads for screw-action fastening or lugs for snap-fastening may be provided to implement the detachable mounting, for example.

A separate needle shield 14 may also be provided for further shielding of the needle and to minimize the risk of contamination. The separate needle shield 14 may be integral with the cap 2. Alternatively, the needle shield 14 may be non-integral with the cap 2, but arranged to interact with the cap 2 (via clips or the like) so that when the cap 2 is removed, the needle shield 14 is also removed.

In Figures 1A to 1C, the auto injector 1 is shown in a fully un-actuated state. The syringe 6 installed in the syringe receiving portion 16 is in a retracted position and has its piston 8 fully withdrawn. The cap 2 and needle shield 14 are in place.

Relative to Figures IA to IC, Figures 2A to 2C illustrate the situation after a user has removed the cap 2 and needle shield 14. The outer member 4 is still in the first position.

Figures 3A to 3C illustrate the situation where a user subsequently presses the auto injector 1 against an injection site ready for actuation of the injection process. The action of pressing the auto injector 1 against the injection site causes the outer member 4 to move forwards into the second position.

Despite the fact that the cap 2 and needle shield 14 have been removed, the needle 18 is still shielded from inadvertent contact with a user, even if the user moves the auto injector 1 away from the injection site, by the end portion 12A of the housing 12, which extends axially beyond the tip 19 of the needle 18. Tn other words, the housing 12 extends further in a direction of injection than the needle 18. The size of the opening 25 (which in the embodiment is in a plane perpendicular to the axis of the syringe) of the leading end portion 12A of the housing 12, and the amount by which the leading end portion 12A of the housing 12 extends beyond the tip 19 of the needle 18, are such that it is not possible for an adult finger to access the tip 19 of the needle 18 while the auto injector 1 is in this state. Of course, the dimensions could be chosen so that it is not possible for a child's finger to access the needle either.

This could be achieved by the making the opening 25 smaller and/or increasing the amount by which the leading end portion 12A of the housing 12 extends beyond the tip 19 of the needle 18. However, where a needle shield 14 is to be used with the device 1, the opening 25 should be large enough to allow the needle shield 14 to be removed.

The action of pressing the auto injector 1 against the injection site involves gripping the outer member 4 and applying a force in an axial direction (right to left in the orientation of the Figures), The leading end portion 12A will come into contact with the injection site first so the result of the force applied via the outer member 4 is a force between the outer member 4 and the housing 12. This force causes the outer member 4 to move against the resilient member 24 from the first position (shown in Figures 1A to 1C) to the second position (shown in Figures 3A to 3C). The extent of travel of the outer member 4 between the first and second positions is shown in Figures 3B and 3C by arrow 26. Relative to the housing 12, the outer member 4 moves in a right to left axial direction.

Thus, the force which causes the auto injector 1 to be pressed into position at the injection site is the same force which causes the outer member 4 to move from the first position to the second position. No separate action from the user is required.

Figures 4A to 4C show the state of the auto injector 1 after the actuation mechanism has been actuated and the injection process is nearly complete (as can be seen from the fact that the plunger 8 has nearly completed its travel within the syringe 6).

The auto injector 1 at this stage should still be in contact with the injection site and the outer member 4 in the second position, as shown in the Figures.

A resilient device 30 (such as a spring) is provided which applies a force to the piston 8 of the syringe 6 in the injection direction. However, prior to actuation of the actuator 10, movement of the piston 8 relative to the housing 12 is prevented by clips (or the like), which lock the piston 8 axially to the housing 12. Actuation of the actuator 10 causes the clips (or the like) to be released and, if the outer member 4 is in the second position, the piston 8 will be free to move in the injection direction under the force provided by the resilient device 30. In the present embodiment, the result of this movement is initially a corresponding axial movement of the lower telescopic body 1 6B (along with the needle 18 and body 20 of the syringe 6). When the lower telescopic body I 6B reaches the end of its allowed travel (when the 0 telescopic body 1 6B again comes into engagement with the outer member 4 in its second position, for example), subsequent axial movement of the piston 8 is effective to dispense fluid out of the syringe 6 through the needle 18. The position of the syringe needle 18 when the lower telescopic body 1 6B is at the end of its allowed travel is such that the needle tip 19 extends beyond the leading end portion l2A of the housing 12 for piercing the skin of the body to be injected.

When the lower telescopic body 1 6B reaches the end of its allowed travel, ramp 32 pushes away clips 12B of the housing 12 that retain the upper telescopic body 16A,

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leaving it free to move. At any point thereafter, release of the outer member 4 (i.e. normally caused by moving the auto injector 1 away from the skin) will cause the whole of the syringe receiving portion 16 and syringe 6, due to the interaction by engaging member 4A, to move axially away from the injection site (i.e. in an axial direction opposite to that in which the needle of the syringe points), as the outer member 4 is pulled by the resilient member 24 from its second position back to the first position.

A disconnection mechanism may be provided for disconnecting the resilient device from the syringe 6 after actuation of the injection process. This disconnection may occur as the syringe plunger 8 reaches the end of its travel. Alternatively, the disconnection may occur at an intermediate time between actuation of the injection process and the plunger 8 reaching the end of its travel. In the latter case, the intermediate time and the force from the resilient device 30 should be arranged such that the injection process will nevertheless be completed. Where the disconnection mechanism is present, the force required of the resilient device 24 is lower, because it does not need to work against the resilient device 30 when pulling the outer member 4 (and syringe 6) back from the second position to the first position (with the syringe 6 moving from the injection position to the retracted position). If the resilient device 24 is weaker, the force with which the auto injector 1 needs to be pressed against the injection site is lower, making the device easier and safer to use.

This situation is illustrated in Figures 5A to 5C. The top telescopic body 16A will reach a higher position within the housing 12 than before actuation because the syringe receiving portion 16 is longer after actuation than before actuation. Clips may be provided to fix the position of the top telescopic body 16A when it reaches the higher position, preventing it being pushed back and thereby ensure the needle 18 stays safely shielded within the leading end portion 12A of the housing 12.

Claims

CLAIMS1. An auto injector for injecting a fluid from a syringe into a human or animal body, the auto injector comprising: a housing; a syringe receiving portion for receiving the syringe within the housing, the syringe receiving portion being configured such that the syringe is moveable relative to said housing between an injection position at which the needle tip of the syringe is exposed for injection to a retracted position at which the needle tip is shielded by the housing; an injection system for carrying out an injection process; and an outer member mounted on said housing so as to be moveable relative thereto between a first position and a second position, the outer member being resiliently biassed towards said first position, wherein said outer member is configured to interact with said syringe receiving portion so that, when said syringe is in the injection position, movement of said outer member from said second position towards said first position causes said syringe to move from said injection position to said retracted position.
2. An auto injector according to claim 1, wherein said syringe receiving portion is configured so that the syringe is moveable relative to said housing in an axial direction, the needle tip is axially outside of said housing when said syringe receiving portion is in said injection position, and the needle tip is axially within said housing when said syringe receiving portion is in said retracted position.
3. An auto injector according to claim 1 or 2, wherein said injection process comprises moving the syringe from said retracted position to said injection position and dispensing the fluid to be injected through the needle.
4. An auto injector according to any one of the preceding claims, further comprising: an actuator by which a user can cause said injection system to carry out said injection process.
5. An auto injector according to claim 4, wherein said outer member is configured so that said actuator is more easily accessible by a user when said outer member is in said second position than when said outer member is in said first position.
6. An auto injector according to claim 4 or 5, wherein said outer member is configured so that said actuator is substantially inaccessible to a user when said outer member is in said first position.
7. An auto injector according to any one of claims 4 to 6, wherein said outer member is configured to cover said actuator when said outer member is in said first position.
8. An auto injector according to any one of claims 4 to 7, wherein said actuator is located on an end of said auto injector axially opposite to that of the needle of a syringe received in said syringe receiving portion, said outer member comprises a sheath substantially radially surrounding said housing, and said outer member is configured so that, when said outer member is in said first position, said sheath extends axially beyond said actuator so as to inhibit access to said actuator by a user.
9. An auto injector according to any one of the preceding claims, wherein said injection system comprises a resilient device for forcing the syringe from said retracted position to said injection position; and a resilient device for forcing movement of a piston of the syringe to cause fluid to leave the syringe via said needle.
10. An auto injector according to claim 9, wherein said outer member is resiliently biassed towards said first position by a force larger than can be provided by the resilient device for forcing the syringe from said retracted position to said injection position and the outer member is configured to interact with said syringe receiving portion such that movement of said syringe from said retracted position towards said injection position cannot occur without a corresponding movement of said outer member from said first position towards said second position.
11. An auto injector according to claim 9, further comprising: a disconnection mechanism for disconnecting from said syringe the resilient device for forcing the syringe from said retracted position to said injection position, after actuation of said injection process, such that said syringe reaches said injection position, but no force is applied to the syringe thereafter by the resilient device for forcing the syringe from said retracted position to said injection position.
12. An auto injector according to claim 11, wherein said outer member is resiliently biassed towards said first position by a force smaller than can be provided by the resilient device for forcing the syringe from said retracted position to said injection position.
13. An auto injector according to any one of the preceding claims, wherein a movement of said outer member in use from said first position to said second position has a component in a direction towards the human or animal body to be injected.
14. An auto injector according to any one of the preceding claims, wherein at least a portion of at least one of said housing, said syringe receiving portion and said outer member is or are sufficiently transparent for a user to be able to obtain information about the amount of fluid that remains in said syringe and thereby the extent to which the injection process has been completed.S
15. An auto injector system comprising an auto injector according to any one of the preceding claims; and a syringe mounted within said syringe receiving portion.
16. A method of using an auto injector, the auto injector comprising: a housing; a syringe receiving portion containing a syringe within the housing, the syringe receiving portion being configured such that the syringe is moveable relative to said housing between an injection position at which the needle tip of the syringe is exposed for injection to a retracted position at which the needle tip is shielded by the housing; an injection system for carrying out an injection process; and an outer member mounted on said housing so as to be moveable relative thereto between a first position and a second position, the outer member being resiliently biassed towards said first position, the method comprising: when said syringe is in the injection position, releasing said outer member so that said outer member moves from said second position to said first position, said outer member being configured to interact with said syringe receiving portion so that the movement of said outer member from said second position towards said first position causes said syringe to move from said injection position to said retracted position.
17. An auto injector constructed and arranged to operate substantially as hereinbefore described with reference to and/or as illustrated in the accompanying drawings.
18. A method of using an auto injector substantially as hereinbefore described with reference to andlor as illustrated in the accompanying drawings.