AUTO-INJECTOR DEVICE EQUIPPED WITH RECONSTITUTION FUNCTIONALITY FOR MULTIPLE CHAMBER DRUG CARTRIDGE

Abstract

Handheld motor-driven drug reconstitution and auto-injector device (1) having a proximal drive system (2) comprising an elongated body (3) housing a controllable drive motor (6), and an axially drivable piston rod (7), and a distal drug cartridge holder assembly (11) housing a multiple chamber (30, 31) drug cartridge (25), the cartridge holder assembly (11) being releasably attached to a distal zone (23) of the drive system (2), the drive system (2) and cartridge holder assembly (11) being configured to impart a movement to the drug cartridge holder assembly (11) in which said drug cartridge holder assembly (11) is moved from a first substantially extended distal configuration along the central longitudinal axis, to a second substantially collapsed proximal configuration along the central longitudinal axis, the relative movement of the drug cartridge holder assembly (11) effecting reconstitution of an injectable product from substances contained in each of the chambers (30, 31).

Claims

1. A handheld motor-driven drug reconstitution and auto-injector device (1) comprising: a proximal drive system (2) comprising: an elongated body (3) having a substantially central longitudinal axis (4) along said elongated body, and a bore (5) extending along said longitudinal axis (4) and within said body (3), the elongated body (3) housing a controllable drive motor (6), and an axially drivable piston rod (7) coupled to said motor (6) located within said bore (5); and a distal drug cartridge holder assembly (11): configured to house within said assembly (11) a multiple chamber drug cartridge (25) comprising at least a first substance stored in a first chamber (30), and at least a second substance stored in a respective second chamber (31), the first and second chambers (30, 31) being located in a nose to tail arrangement in substantial axial alignment with the central longitudinal axis (4); wherein the distal drug cartridge holder assembly (11) has a proximal extremity (16, 19) which is releasably attached to a distal zone (23) of the proximal drive system (2), and a distal extremity (34) configured to receive an injection needle; the proximal drive system (2) and distal drug cartridge holder assembly (11) being configured to impart a movement to the drug cartridge holder assembly (11) in which said drug cartridge holder assembly (11) is moved from a first substantially extended distal configuration along the central longitudinal axis, to a second substantially collapsed proximal configuration along the central longitudinal axis; and wherein the relative movement of the drug cartridge holder assembly (11) as it is moved along the longitudinal central axis (4) by the drive system (2), from the first substantially extended distal configuration to the second substantially collapsed proximal configuration effects reconstitution of an injectable product comprising the at least first and second substances located within only one of said at least first or second chambers (30, 31) after said reconstitution.

2. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, wherein the cartridge holder assembly (11) is further configured to be operated by the proximal drive system (2) in a reversed relative movement compared to reconstitution movement, to move the components of the cartridge holder assembly (11) from a proximal, collapsed configuration to a distal, extended configuration.

3. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, wherein the movement of the drug cartridge holder assembly (11) from the extended configuration to the collapsed configuration includes a telescopic movement.

4. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, wherein the movement of the drug cartridge holder assembly (11) from the extended configuration to the collapsed configuration includes both a rotational telescopic movement and a translational telescopic movement.

5. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, wherein the drug cartridge holder assembly (11) comprises a plurality of interconnected elongated hollow bodies (13, 14, 15) in concentric axial alignment about the longitudinal central axis (4).

6. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, wherein the drug cartridge holder assembly (11) comprises: a first elongated body (13) comprising a bore (13A) in axial alignment with the longitudinal axis; a second elongated body (15) comprising a bore (15A) in axial alignment with the longitudinal axis; and a third elongated body (14) comprising a bore (14A) in axial alignment with the longitudinal axis, the three elongated bodies (13, 14, 15) being interconnected and organised in concentric axial alignment about the longitudinal central axis (4).

7. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, wherein: a first elongated body (13) of the drug cartridge holder assembly and a third elongated body (14) of the drug cartridge holder assembly are connected respectively to one another via a contact surface comprising an inner surface (18) of the first elongated body (13), and outer surface (36) of the third elongated body (14); when driven by the drive system (2), the configured permitted movement of the third elongated body (14) relative to the first elongated body (13) of the drug cartridge holder assembly (11) is a rotational movement about the longitudinal axis (4) and along the contact surface (18, 36) in a proximal direction.

8. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, wherein: a second elongated body (15) of the drug cartridge holder assembly (11) is located concentrically around, and extends in a distal direction from a proximal extremity (19) over a first elongated body (13) to a distal extremity (20); the distal extremity (20) of the second elongated body (15) of the drug cartridge holder assembly (11) is located concentrically around, and extends over, at least a proximal extremity (33) of a third elongated body (14) of the drug cartridge holder assembly (11); and when driven by the drive system (2), the configured permitted movement of the third elongated body (14) relative to the second elongated body (15) of the drug cartridge holder assembly is a translational movement along the longitudinal axis (4) in a proximal direction inside a bore (15A) of the second elongated body (15).

9. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, wherein: a first elongated body (13) of the drug cartridge holder assembly (11) and a second elongated body (15) of the drug cartridge holder assembly (11) are connected respectively to one another via a contact surface comprising cooperating interlocking means (51, 52) provided respectively on the second elongated body (15) and on the first elongated body (13); the respective cooperating interlocking means (51, 52) are configured to allow relative rotational movement of the first elongated body (13) within a bore (15A) of the second elongated body (15); and when driven by the drive system (2), the respective interlocking means (51, 52) cooperate to cause the first elongated body (13) to rotate about the longitudinal axis (4) within the bore (15A) of the second elongated body (15).

10. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, further comprising a coupling member (40) configured to couple a proximal extremity (16) of the drug cartridge holder assembly (11) to the axially drivable piston rod (7) of the drive system (2), wherein: the coupling member (40) comprises an elongated body (41) having a bore (42) in axial alignment with the longitudinal axis (4) and housed within the elongated body (3′,3″) of the drive system (2); the coupling member (40) and drivable piston rod (7) are connected to each other via corresponding piston drive engagement means (46, 53, 54, 55, 58) provided respectively in, or on, the elongated body (41) of the coupling member (40) and the drivable piston rod (7); when driven by the drive system (2), the respective piston drive engagement means (46, 53, 54, 55, 58) cooperate to cause the coupling member (40) to rotate freely within the elongate body (3′, 3″) of the drive system (2).

11. (canceled)

12. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, comprising a piston drive engagement means (53, 54, 55, 58) located on the drivable piston rod (7) configured to be automatically biased in a proximal direction after injection, or removal of the cartridge holder assembly after reconstitution, by a biasing member (45) located in, or on, a coupling member (40) configured to couple a proximal extremity (16) of the drug cartridge holder assembly (11) to the axially drivable piston rod (7) of the drive system (2).

13. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1 wherein a coupling member (40) configured to couple a proximal extremity (16) of the drug cartridge holder assembly (11) to the axially drivable piston rod (7) of the drive system (2) comprises distal engagement means (48) configured to engage with a proximal extremity (16) of a first elongate body (13) of the cartridge body holder assembly (11); when driven by the drive system (2), the distal engagement means (48) of the coupling member (40) are configured to cause a rotation of an elongate body (40) of the coupling member about the longitudinal axis (4) to be transmitted to a first elongate body (13) of the cartridge holder assembly (11).

14. (canceled)

15. The handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1, wherein the drug cartridge holder assembly (11) is releasably attached to a distal zone (23) of the drive system (2) via respectively cooperating surfaces (22, 24) provided on the body of the drive system (2) and an elongated body (15) of the drug cartridge holder assembly (11).

16. A process for the reconstitution of an injectable product contained in a multiple-chamber drug cartridge (25) of an auto-injector device (1), comprising at least a first substance stored in a first chamber (30), and at least a second substance stored in a respective second chamber (31), the first and second chambers (30, 31) being located in a nose to tail arrangement in substantial axial alignment with a central longitudinal axis (4) of the auto-injector device (1), comprising: providing a handheld motor-driven drug reconstitution and auto-injector device (1) according to claim 1; activating a function of said auto-injector device (1) involving at least a reconstitution step prior to injection; wherein the reconstitution step comprises driving a drive motor (6) of said device to cause relative movement of a drug cartridge holder assembly (11) along the longitudinal central axis (4) of the device (1), from a first substantially extended distal configuration to a second substantially collapsed proximal configuration, thereby effecting reconstitution of the injectable product within only one of said at least first or second chambers (30, 31).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG. 1 represents a schematic exploded perspective view of a motor-driven auto-injector and reconstitution device according to the invention;

[0058] FIG. 2 represents a first schematic cross-section view of the device of FIG. 1, before reconstitution;

[0059] FIG. 3 represents a first schematic cross-section view of the device of FIG. 1, after reconstitution;

[0060] FIG. 4 represents an alternative schematic cross-section view of the device of FIG. 1, before reconstitution;

[0061] FIG. 5 represents an alternative schematic cross-section view of the device of FIG. 1, after reconstitution.

[0062] FIGS. 1 to 5 represent different schematic views of a device according to the invention. FIGS. 4 and 5 differ from FIGS. 2 and 3 mainly in the fact that the cross-section illustrated represents a 90° rotation of the device along a longitudinal axis thereof. Other than that, all elements remain the same as in FIGS. 2 and 3 and are numbered accordingly.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0063] Turning now to FIG. 1, a handheld motor-driven drug reconstitution and auto-injector device (1) according to the invention is represented schematically in an exploded perspective view. The device (1) comprises a drive system (2) comprising an elongated body (3′, 3″) made up of a proximal part (3′) and a distal part (3″) the proximal and distal parts fitting and interlocking together to form the elongated body (3′, 3″), and having a substantially central longitudinal axis (4) along said elongated body (3′, 3″). A bore (5) extends along said longitudinal axis (4) and within said body (3′, 3″), the elongated body (3′, 3″) being advantageously enclosed, for example, by two further complementary covers (3A, 3B), which can be fixed together for example by gluing, ultrasonic welding, clipping, of push-fitting together of the two halves (3A, 3B). Preferably, the elongated body (3′, 3″) is integrally moulded by injection moulding, for example. The elongated body (3′, 3″) houses a controllable drive motor (6), and an axially drivable piston rod (7) coupled to said motor (6) located within said bore (5). The controllable drive motor is controlled by a controller (8) usefully located on a printed circuit board (9) and appropriately housed within one of the complementary covers (3A, 3B). The controller (8) is a programmable controller such as an EEPROM or other suitable programmable controller, for example a microcontroller, of the type generally known in the art. The controller (8) can integrate, or be connected to, other electrical or electronic components, for example: a power supply such as a battery, optionally rechargeable, or a lithium ion type battery; one or more communications circuits, for example a near-field communications circuit, an RFID circuit, and/or a Bluetooth® communications circuit, such as a Bluetooth® LE circuit for low energy consumption; one or more memory storage components for storing data, including, for example, volatile and/or non-volatile memory storage; one or more sensors connected to the controller for capturing data from the auto-injector device or drive system; one or more display components, configured to display values, or signals, such as visual signals, representing data or functional states of the device, such as an LCD display; one or more user input components configured to enable user input to the device, for example for setting a dose to be administered; and one or more switches for activating or deactivating other components within the device, for example, a proximal button (10) located and seated at the proximal end of the elongated body of the drive system connected to the controller (8) and configured to activate the motor (6) to drive the piston rod (7). The communications circuits are configured, for example, for transmitting information from the auto-injector and reconstitution device (1) to a remote data gathering and processing device, such as a remote or distributed computing system, or for example, a smartphone via a correspondingly programmed application, or to be stored on, or transmitted by, any other kind of mobile telecommunications device, but are also usefully configured to receive information from such remote data gathering and processing devices. As can be seen from FIG. 1, the bore (5) of elongated body (3′, 3″) houses, along with other components as described herein, the motor (6), and threaded piston rod (7) in axial alignment within the bore (5). The bore (5) is closed by the proximal button (10) which is seated in, and covers, the proximal extremity of the bore (5).

[0064] The device (1) further comprises a drug cartridge holder assembly (11). A distal cap (12) is provided to cover the cartridge holder assembly (11) when the latter is mounted to the drive system (2). The cartridge holder assembly comprises three elongated bodies (13, 14, 15) each comprising a bore (13A, 14A, 15A) extending along the longitudinal axis (4). A first elongated body (13), having a proximal extremity (16) and a distal extremity (17) is connected at its proximal extremity (16) to a distal zone of the drive system (2) as will be described herein. The first elongated body (13) has a screw threaded contact surface (18) on an inner surface of the bore (13A) which extends substantially all the way along the bore (13A) from the distal extremity (17) to the proximal extremity (16). A second elongated body (15) having a proximal extremity (19) and a distal extremity (20) has a bore (15A) of greater diameter than either the first elongated body (13) or the third elongated body. In FIG. 1, in the exploded view, the second elongated body (15) is shown distally of both the first and third elongated bodies (13, 14), however, it should be understood that both the first (13) and third (14) elongated bodies are arranged coaxially and concentrically within the bore (15A) of the second elongated body (15) of the cartridge holder assembly (11), and that the second elongated body (15) essentially extends over the whole length of the first elongated body (13). Located adjacent to the proximal extremity (19) of the second elongated body (15), and on the outer surface (21) of the body (15) is a screw thread (22). The screw thread (22) of second elongated body (15) is configured and dimensioned to enable engagement of the second elongated body (15) with a distal area or zone (23) of the distal part of the body (3″), and in particular a screw thread (24) provided on an inner surface of the body (3″) facing inwards into the bore (5). Screw thread (24) and screw thread (22) interact and complement each other to form an engagement contact surface that enables the cartridge holder assembly (11) to be removably mounted to the drive system (2), by screwing the cartridge holder assembly into the distal zone of the drive system (2). Additionally, optional corresponding abutment projections are advantageously provided on an inner and/or corresponding outer surface of the elongated bodies (13, 14, 15) in order to facilitate and/or effect longitudinal and axial, and/or respectively superimposed, alignment of optionally provided viewing windows in each of the first and third elongated bodies (13, 14).

[0065] Before mounting of the cartridge holder assembly (11) to the distal zone (23) of the drive system (2), and in particular to the distal zone of body (3″), a multiple chamber drug cartridge (25), for example, a dual chamber drug cartridge containing at least a first and second substances to be reconstituted into an injectable product, is inserted axially into the cartridge holder assembly (11) through the bore (13A) of first elongated body (13). The dual chamber drug cartridge (25), for example, made of glass, as shown in FIG. 1 has a proximal extremity (26) and a distal extremity (27), and defines a bore in a known manner in which a first proximal stopper (28) is located at, or substantially adjacent to, the proximal extremity (26) and a second stopper (29) located distally of the first stopper (28) along the bore, thereby forming a first chamber (30). The first chamber (30) comprises a first substance or component of the drug to be reconstituted, for example a solvent. The second stopper (29) furthermore defines a second chamber (31) in the volume that lies distally of the second stopper (29) and between the second stopper (29) and the distal extremity (27) of the cartridge (25). The second chamber (31) contains the second substance or component to be reconstituted, for example a solute powder that is soluble in the solvent, when the components are reconstituted. The first (30) and second chambers (31) are interconnected by a bypass (32), formed as a narrow conduit or passage between the two chambers, and in the initial positions of the stoppers, before reconstitution is operated, the bypass (32) is closed by the second stopper (29), thereby preventing the coming into contact of the first and second substances with each other.

[0066] A third elongated body (14) is coaxially and concentrically seated within the bore (13A) of the first elongated body (13). The third elongated body (14) has a proximal extremity (33) and a distal extremity (34). When the drug cartridge is inserted in the holder assembly (11), the distal extremity (27) of the drug cartridge (25) comes to rest, and is engaged, by a neck (35) provided at the distal extremity (34) of the third elongated body (14). The proximal extremity (33) of the third elongated body (14) is provided with a screw threading (36) on an outer surface (37) of the elongated body (14). This screw-threading (36) runs counter directionally to the screw-thread (18) provided on the inner surface of the first elongated body (13), such that when the two screw threads (18, 36) engage each other, for example, through rotation of the first elongated body caused by driving of the motor and threaded piston, the third elongated body is withdrawn into the bore (13A) of the first elongated body (13), moving relative thereto in a proximal direction. At the same time, the third elongated body (14) translates along the bore (15A) of the second elongated body. The third elongated body (15) is provided with an inwardly facing annular shoulder or projection (38), located at its distal extremity (20), which overlaps at least partly with the third elongated body (14) in the initial expanded configuration of the cartridge holder assembly (11). Undesired distal movement of the third elongated body (14) is prevented by engagement of the projecting annular shoulder (38) of the second elongated body (15) with an outwardly projecting abutment (39) provided on the outer surface of the third elongated body.

[0067] The auto-injector and reconstitution device (1) further comprises a coupling member (40), configured and dimensioned to rotationally couple the cartridge holder assembly (11) to the drivable drive piston (7). The coupling member comprises an elongated body (41) having a bore (42), a proximal extremity (43) and a distal extremity (44). The elongated body (41) has a portion (41A) of narrower diameter extending from the proximal extremity at least partially along the length of the body (41), for example approximately half way along the length of the body (41). The narrower diameter portion (41A) provides room to accommodate a biasing member (45), such as a coiled spring, located coaxially around an outside surface of said narrowed diameter portion (41A), and seated against a distal extremity of the narrower diameter portion which forms a radially projecting shoulder (47), cf. FIG. 4. The narrower diameter portion (41A) also comprises at least one longitudinal slot (46), and preferably two such slots, preferably diametrically opposed, extending in parallel along the longitudinal axis (4) from the proximal extremity (43) to the distal extremity and shoulder (47) of the portion of narrower diameter (41A). At the distal extremity (44) of the coupling member (40), a plurality of tongues or splines extending in parallel along the longitudinal axis (4), and radially distributed about said axis, are provided. The splines or tongues (48) are configured and dimensioned to engage, and interlock, with correspondingly dimensioned and configured grooves (49), located at the proximal extremity (16) of the first elongated body (13) of the cartridge holder assembly (11), on an inner surface (50) of said body (13) facing inwardly into the bore (13A) thereof. Upon mounting of the cartridge holder assembly to the drive system, such as by screwing the second elongated body (15) into the distal zone (23) of the drive system, the interlocking of the splines or tongues (48) of the coupling member (40) with the grooves (49) of the first elongated body (14) causes the coupling member (40) and the first elongated body (13) to be rotationally locked, meaning that any rotation imparted to the coupling member is transmitted to the first elongated body of the cartridge holder assembly for as long as said body (13) is physically capable of rotating in the direction of rotation applied by the motor via the piston rod (7).

[0068] Turning back now to the cartridge holder assembly, the first elongated body (13) is mounted, and held within, the bore (15A) of the second elongated body (15). The first elongated body (13) is provided with interlocking engagement means that interlock with the third elongated body (15) to prevent relative distal or proximal movement between the two bodies (13, 15). Such interlocking means are also configured to allow first elongated body (13) to rotate about the longitudinal axis. An example of suitable interlocking engagement means can be an annular projecting shoulder (51), extending from, or adjacent the proximal extremity (16) of the first elongated body of the cartridge holder assembly, and which engages in a correspondingly dimensioned and configured annular groove (52) provided at, or adjacent to, the proximal extremity (19) of the third elongated body of the cartridge holder assembly. In this way, the first elongated body (14) of the cartridge holder assembly (11) is free to rotate within the bore (15A) and yet prevented from movement in a distal and proximal direction along the longitudinal axis (4).

[0069] The threaded piston (7) has a screw thread (53) provided on an outer surface of the piston (7). The piston (7) further comprises a nut (54), provided with an inner threading (55) that runs counter to the threading of the piston (7). The proximal extremity (56) of the nut (54) rests against a distal extremity (57) of the motor (6) in the device (1) before use. Rotating the threaded piston (7) causes the nut (54) to move in a distal direction away from the distal extremity (57) of the motor (6), due to the engagement of the inner threading (55) of the nut (54) with the outer threading (53) of the piston (7). In order to prevent the threaded nut from causing the threaded piston to simply extend to the end of the threading when the motor is activated, for example, by pressing the button switch (10) after having set a dose via the controller (8) to reconstitute and auto-inject, the threaded nut is also provided with a plurality of radially outwardly projecting wings (58), located at the proximal extremity (56) of the nut (54). The wings (58) are configured and dimensioned to engage with the parallel and radially distributed or opposing slots (46) provided on the coupling device. As the nut (54) is constrained rotationally by the interaction of the wings (58) against the slots (46), this results in a rotational force about the longitudinal axis being applied to the coupling member (40). In turn, and because the coupling member (40) is attached to the first elongated body (13) of the cartridge holder assembly (11), this is also brought into rotation. Further rotation of the threaded piston via the drive motor causes the nut (54) to move distally with the wings (58) in the slots (46) against the biasing member (45). Rotation of the coupling member (40), transmitted to the first elongated body (13) of the cartridge holder assembly, causes the internal threading of body (13) to contact the external thread of the third elongated body (14), and thereby withdraw said third body (14) into the bore (13A) of first elongated body (13). This movement in a proximal direction of the third body (14) proceeds until the proximal extremity (33) of the third body (14) comes into abutting contact with an inwardly projecting annular shoulder (59) provided within the bore (13A) of the first body (13) and extending from an inner surface of said body (13) into the bore. Once the third elongated body (14) of the cartridge holder assembly has reached the maximum permitted proximal travel distance, it can no longer rotate. Similarly, body (13) can no longer rotate either, and neither can coupling member (40). The cartridge holder assembly is now fully in the collapsed configuration (cf. FIGS. 3 and 5).

[0070] Subsequently, the threaded piston continues to drive the nut (54) in a distal direction, leading to the distal extremity (60) of the nut (54) coming into contact with the first stopper (28). The distal extremity (60) of the nut (54) can advantageously be provided with a cap or insert (61) made out of rubber, elastomer, or a similarly appropriate plastic material, to form a bearing surface of the nut (54) at the distal extremity (60) thereof against the first stopper (28).

[0071] Continued activation of the drive motor forces the nut (54) and extremity (60) to advance in a distal direction, pushing the first stopper (28) and the contents of the first chamber (30) in a distal direction. The pressure build up caused by the compression of the contents in the first chamber (30) as the first stopper is moved distally by the nut (54) causes the second stopper (29) to be moved distally as well, until it too has moved beyond a proximal entry (62) of the bypass (32). Once the proximal entry (62) of the bypass (32) has been exposed to the substance in the first chamber, and under continued distal movement of first stopper caused by continued distal movement of the nut (54), the substance in the first chamber, e.g. a solvent liquid, is pushed via the first bypass entry through the bypass (32) into the second chamber, and reconstitution of the two substances is allowed to proceed. The first stopper (28) is continuously pushed via the motor (6), and nut (54) in a distal direction within the drug cartridge until all of the first substance has been forced via the bypass (32) into the second chamber (31) and reconstitution has been effected. An injection needle can now be mounted to the distal extremity (34) of the third elongated body (14) of the cartridge holder assembly, and injection allowed to proceed as per the usual command and control of such auto-injector devices.

[0072] Once injection has been completed, and the cartridge now correspondingly empty of any injectable product that was contained therein, the motors direction of rotation can be reversed via the controller and activation button, for example. Reversal of the motors direction causes the nut to move in a proximal direction once more back towards the distal extremity (57) of the motor. In addition, the biasing member (45) pushes against the wings (58) of the nut (54) to facilitate moving the nut (54) backwards in the proximal direction. As movement in the proximal direction progresses, the nut (54) will reach a position where the coupling member (40) and first elongated body (13) of the cartridge holder assembly (11) will once again be free to rotate, under the influence of the wings, this time in an opposite direction to that required for reconstitution, and in doing so, will cause the third elongated body (14) to move in a distal direction once again, taking the cartridge holder assembly (11) from the collapsed state to the extended state. The distal movement of the third elongated body (14) will eventually be halted by the projecting annular shoulder (38) of the second elongated body (15) coming into abutting contact with the outwardly projecting abutment (39) provided on the outer surface of the third elongated body (14). At this point, the nut (54) will have returned to its initial starting position, and the cartridge holder assembly (11) will have reached its initial extended configuration. The cartridge holder assembly (11) can then be removed, and the spent cartridge replaced with a new one to recommence the sequence of reconstitution and injection.