Patent Publication Number: US-2021170106-A1

Title: Assistive device for use with a syringe

Description:
FIELD OF THE INVENTION 
     The present disclose relates to an assistive device for use with a syringe, in particular a syringe prefilled with a medicament. The assistive device serves to improve the handling of the syringe. The device may conceal the syringe and, in particular, the needle, in order to help users not being confident with handling a needle. The assistive device may simplify placing the dispensing end of the device correctly on the skin and administering the medicament. 
     BACKGROUND 
     U.S. Pat. No. 9,233,213 B2 discloses a palm-activated drug delivery device for dispensing medicament from a pre-filled barrel. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present disclosure to provide an assistive device for use with a syringe, the assistive device having improved properties. Specific embodiments may provide increased user comfort, increased user safety, reduced error-proneness and/or reduced manufacturing costs. 
     A first aspect of the present disclosure relates to an assistive device for use with a syringe. The syringe may be a traditional syringe prefilled with a medicament. The syringe may comprise a needle and a barrel containing the medicament. The syringe may be usable as a stand-alone syringe, i.e., without the assistive device. Such a syringe typically comprises a plunger being partially accommodated in the barrel and protruding out of the barrel. The plunger is movable in a distal direction for pressing the medicament out of the barrel. A flange may be located at a proximal end of the barrel for providing a counter bearing for a user&#39;s fingers when using the syringe without the assistive device. 
     In general, the term “distal” or “distal end” refers to that portion or end of the device or a component thereof that is closest to a dispensing end of the device. The dispensing end is the part of the device through which the medicament is dispensed from the device. The term “proximal” or “proximal end” refers to that portion or end of the device or a component thereof that is furthest away from the dispensing end of the device. The term “distal direction” or “distally” refers to the direction defined by a direction from the proximal end to the distal end of the device or a component. The term “proximal direction” or “proximally” refers to the opposite direction, i.e., is defined by a direction from the distal end to the proximal end. 
     The device comprises a housing for accommodating the syringe. The housing may be an outer housing which is held by a user when operating the device. The housing may comprise a distal housing and a proximal housing. The distal and proximal housing may be releasably or unreleasably coupled to each other. In specific embodiments, the housings may be coupled releasably to each other before operation of the device and may be unreleasably locked to each other after operation of the device. 
     The device comprises a dispense member to be moved in a distal direction for dispensing the medicament from the syringe. The movement of the dispense member may be accomplished by manually applying a force on a proximal surface of the dispense member. 
     The dispense member may have an initial, proximal position before starting a dose dispense operation. During dispensing a dose, the dispense member may be moved from the proximal position in a distal direction until a stop is reached and the dispense member cannot be moved further in the distal direction. In specific embodiments, this position of the dispense member may be the final, distal position. 
     The dispense member may directly act on the syringe plunger. For this aim, the dispense member may comprise a post extending from a proximal end of the dispense member in a distal direction and acting on the proximal surface of the plunger for pushing the plunger forwards. The amount of axial movement of the dispense member and the plunger during a dispense operation may be identical. 
     The device comprises a needle guard for covering a needle of the syringe before operation of the device. In this state, the needle guard may be in an initial, distal position. For initiating a dispense operation, the needle guard is movable from the initial distal position in a proximal direction to expose the needle such that the needle protrudes out of a distal end of the device. This is achieved by a user placing the dispensing end of the device on his/her skin and pressing the device towards the skin. This action may push the needle guard in a proximal direction relative to the housing, thereby exposing the needle, which pierces the skin. When the needle guard has been fully pushed in the proximal direction it reaches a stop and cannot move further in the proximal direction. In specific embodiments, this position may be the final proximal position. 
     The assistive device may have different states. In particular, the device may have a locked state, which is present before a dispense operation has been carried out. In the locked state, the dispense member is locked such that a movement of the dispense member in a distal direction is disabled. Thereby, inadvertent dispense of the medicament can be prevented. This may include cases where the device has not yet been positioned at an injection side and the needle has not been exposed. 
     In particular, the dispense member may comprise a first locking device and the housing may comprise a second locking device for locking the dispense member to the housing. The locking devices may interact with each other to lock the dispense member to the housing prior to a proximal movement of the needle guard. 
     The locking may be achieved without any interaction with further components such as the needle guard. In particular, the needle guard may be not in contact with the dispense member in the locked state. As an example, the needle guard may be positioned at a distance from the dispense member. In particular, the proximal end of the needle guard may be located at a more distal position than the distal end of the dispense member. 
     In particular, the housing may comprise a proximal housing and a distal housing to be connected to each other for assembly of the device. The proximal housing may be part of a proximal assembly that also comprises the dispense member. The distal housing may be part of a distal assembly that also comprises the needle guard. For assembly of the device, the syringe may be placed first in the distal assembly and then the proximal assembly may be coupled to the distal assembly. The proximal housing may comprise the second locking device. In this case, the dispense member may be locked with the proximal housing also prior to assembly of the device. Accordingly, the locking may be already present in a pre-assembled state of the device. 
     Thereby, the assembly of the device may be simplified, because the dispense member is not a movable part in the proximal assembly. In specific embodiments, neither the proximal assembly nor the distal assembly comprises any parts movable to the respective housing before assembly of the proximal housing with the distal housing. 
     The device may comprise a release device for unlocking the locking devices and, thereby, the dispense member, when the needle guard has moved in a proximal direction. In particular, the needle guard may have a most distal position and a most proximal position relative to the housing and the unlocking may occur when the needle guard is in or near its most proximal position. 
     In specific embodiments, the needle guard may comprise the release device for unlocking the dispense member. When the dispense member is in its unlocked state, the first locking device may no longer interact with the second locking device. In this state, the dispense member is movable in the distal direction. 
     The dispense member may comprise a flexible component providing the first locking device. In particular, the flexible component may have the shape of a flexible arm. The flexible arm may extend from a proximal part of the dispense member in a distal direction. 
     In the assembled device, the flexible arm may be permanently biased away from its relaxed state. In particular, a tip of the flexible arm may be flexed inwards from its relaxed state by abutment with the housing or the needle guard, depending on the state of the device. Accordingly, the tip may exert an outwardly directed counterforce on the housing or the needle guard, respectively. The flexible arm, in particular the tip of the flexible arm may interact with the housing to lock the dispense member as long as the needle guard is in its distal position. 
     The interaction of the first and second locking devices may be an abutment of the first locking device on the second locking device, in particular an abutment of a distal face of the first locking device on a proximal face of the second locking device. The second locking device may comprise a protrusion. The protrusion may be an inwardly directed protrusion at an inner surface of the housing. The protrusion may have the shape of a ledge. 
     The device may comprise several first locking devices and several second locking devices. As an example, the dispense member may comprise two flexible arms and the housing may comprise two protrusions located at opposite sides of the device. 
     The release device may interact with the first locking device of the dispense member, in particular move the first locking device out of interaction with the second locking device. In particular, the release device may push the first locking device inwardly. This may lead to the first locking device being not located above the second locking device anymore such that a movement of the dispense member is not blocked by an abutment on a proximal face of the second locking device. The release device may be provided by a rigid, i.e. non-flexible part. The release device may have a slot to receive the second locking device when moving in a proximal direction. 
     As an example, the needle guard may comprise a rack. The rack may extend in the proximal direction. The release device may be provided by the rack. In particular, a tip portion of the rack may interact with the first locking device. The needle guard may comprise several racks. As an example, the needle guard may comprise two racks located on opposite sides of the device. 
     For unlocking the dispense member, the release device may slide between the housing and the first locking device when the needle guard moves in a proximal direction. The first locking device may have a surface for interaction with a surface of the release device. Both surfaces may be beveled to facilitate the interaction. In addition to that, the first locking device may have a protruding portion serving as a spacer to provide a gap between the surface for interaction with the release device and the inner wall of the housing. The spacing facilitates the sliding of the release device between the housing and the surface of the dispense member. 
     When the dispense member and the housing are unlocked from each other, the device is in an operational state ready to dispense. For dispensing the medicament, the dispense member can now be pushed in a distal direction. 
     In specific embodiments of the device, the dispense member may be retained in its position during a dispense operation, when the dispense member is inadvertently released. In this regard, during a dispense operation means that the dispense member has not arrived at a final distal position but is still movable distally. As an example, flexible arms of the dispense member may be pretensioned during a dispense operation such that they exert a counterforce on a part of the device, which holds the dispense member in its position. In particular, the flexible arms may slide along the needle guard during a distal movement of the dispense member. 
     In specific embodiments, the device is a single-use device such that only a single dispense operation is enabled. The single dispense operation includes a movement of the dispense member in a distal direction until a stop is reached. The device may have a locked-out state, in which a further dose dispense operation is disabled. 
     In an embodiment, the device may be configured such that when the needle guard is in its proximal position and the dispense member is in its distal position, the needle guard interacts with the dispense member such that the dispense member and/or the needle guard is held in its axial position. In particular, the positions of the needle guard and the dispense member at the end of a dose dispense operation may be maintained. 
     As an example, the needle guard may comprise a first lock-out device and the dispense member may comprise a second lock-out device. 
     The lock-out devices may engage each other at or near the end of a dose dispense operation. As an example, the first lock-out device may comprise an inwardly directed protrusion. The second lock-out device may comprise an opening for engagement with the protrusion, or vice versa. In particular, a flexible arm of the dispense member may provide the second lock-out device. Accordingly, the flexible arm may both provide the locking device for locking the dispense member prior to a dispense operation and the lock-out device for locking the dispense member after a dispense operation. The locking device and the lock-out device may overlap with each other. 
     As a further example, lock-out may be provided by friction between the needle guard and the dispense member. In particular, friction may be present between a flexible arm of the dispense member acting on the needle guard. 
     In the locked state, the dispense member may remain in its most distal position. Furthermore, the needle guard may remain in its retracted position such that the needle remains exposed. In other words, the needle may be permanently visible after dispense of the medication and release from a user&#39;s skin. This may clearly signal to a user that the device has been used and should be discarded. 
     In addition to that, in the locked-out state also a re-use of the syringe may be prevented. In particular, a disassembly of the device may be prevented when the dispense member is locked to the needle guard. Accordingly, a disconnection of the proximal housing from the distal housing may be disabled after dispense of a medication. Also here, locking means that relative movements between the parts, in particular relative axial movements are prevented. Thereby, safety may be increased. 
     In specific embodiments, the device does not comprise a longitudinally acting spring. As an example, the device is free from a longitudinally acting spring being pretensioned to move the needle guard back or the dispense member in its distal position after use. Among others, this reduces the production costs of the device. 
     According to a second aspect of the present invention, an assistive device for use with a syringe comprises a housing for accommodating the syringe, a dispense member to be moved in a distal direction for dispensing a medicament from the syringe and a needle guard having a distal position for covering a needle of the syringe before operation of the device, wherein the needle guard is moveable from the distal position to a proximal position to expose the needle. The assistive device is configured such that when the needle guard is in its proximal position and the dispense member is in its distal position, the needle guard interacts with the dispense member such that the dispense member and/or the needle guard is held in its axial position. 
     The device according to the second aspect may comprise any structural and functional features described in the foregoing in relation to the assistive device of the first aspect. However, the device according to the second aspect is also independent from the subject matters of first and second locking devices. 
     As an example, the needle guard may comprise a first lock-out device and the dispense member may comprise a second lock-out device engaging each other for locking the needle guard to the dispense member. The second lock-out device may comprise an opening for engagement with the protrusion, or vice versa. This locking may occur at the end of a dose dispense operation. 
     As a further example locking may be achieved by a frictional force between the dispense member and the needle guard. In particular, a flexible arm of the dispense member may exert a resilient force on the needle guard. 
     According to a further aspect, a medication delivery kit is disclosed, the medication delivery kit comprising the assistive device and a prefilled syringe accommodated in the assistive device. In particular, the syringe may be filled with a pharmaceutical preparation comprising fremanezumab, an anti-calcitonin gene-related peptide (anti-CGRP) monoclonal antibody for the preventive treatment of migraine. 
     The medication delivery kit may comprise any structural and functional feature described in the foregoing in relation to the assistive devices and the syringe. The assistive device and prefilled syringe may be packaged or otherwise distributed together. In the assembled state of the assistive device and prefilled syringe, the medication delivery kit is also denoted as medication delivery device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
       Features which are described herein above and below in conjunction with different aspects or embodiments, may also apply for other aspects and embodiments. Further features and advantageous embodiments of the subject-matter of the disclosure will become apparent from the following description of the exemplary embodiment in conjunction with the figures, in which: 
         FIG. 1  shows an embodiment of an assistive device in a side view. 
         FIG. 2  shows the assistive device of  FIG. 1  in a pre-assembled state and a syringe to be used with the device. 
         FIG. 3  shows an exploded view of the assistive device of  FIG. 1  and the syringe. 
         FIGS. 4A to 4C  show a proximal assembly of the device of  FIG. 1  in a side view, a top view and a longitudinal-sectional view, respectively. 
         FIGS. 5A to 5C  show a dispense member of the assistive device of  FIG. 1  in a side view, a rotated side view and a longitudinal-sectional view, respectively. 
         FIGS. 6A to 6E  show a distal housing of the assistive device of  FIG. 1  in a perspective view, a side view, a rotated side view, a top view and a longitudinal-sectional view, respectively. 
         FIGS. 7A to 7E  show a needle guard of the assistive device of  FIG. 1  in a perspective view, a side view, a rotated side view, a top view and a longitudinal-sectional view, respectively. 
         FIGS. 8A to 8D  show a protective cap of the assistive device of  FIG. 1  in a perspective view, a side view, a top view and a longitudinal-sectional view, respectively. 
         FIGS. 9A to 9C  show the assistive device of  FIG. 1  comprising a syringe in different states in longitudinal-sectional views, wherein: 
         FIG. 9A  shows the assistive device in a locked state of the dispense member prior to use. 
         FIG. 9B  shows the assistive device in an unlocked state of the dispense member, ready to dispense. 
         FIG. 9C  shows the assistive device in a locked-out state after usage. 
     
    
    
     Like elements, elements of the same kind and identically acting elements may be provided with the same reference numerals in the figures. 
     DETAILED DESCRIPTION 
       FIG. 1  shows an assistive device  1  for use with a syringe  2 . The syringe  2  is accommodated in a housing  3  of the device  1 . The syringe  2  is concealed by the housing  3  and is indicated with a dashed reference line. The syringe  2  is explicitly shown in  FIG. 2 , for example. The housing  3  may have a cross section area in the range of about 4 cm2 to about 16 cm2, for example. 
     The assistive device  1  assists a user in holding and operating the syringe  2  for administering a medicament. Accordingly,  FIG. 1  also shows a medication delivery device  4  comprising the assistive device  1  and the syringe  2 . 
     Embodiments of the device  1  provide a pre-use locking mechanism such that an inadvertent dispense operation is prevented. Additionally or alternatively, embodiments of the device  1  provide a lock-out mechanism such that a re-use of the device  1  after use is disabled. In particular, the device  1  may be a single-shot device, allowing only a single dispense operation. Such devices may be also called single-use devices. 
     The assistive device  1  has a centerline  5 , a proximal end  6  and a distal end  7 . The housing  3  accommodates the syringe  2  and is held by a user when operating the device  1 . The syringe  2  is fixed within the housing  3  such that any relative movements between a main part of the syringe  2  and the housing  3  are disabled. The housing  3  comprises a proximal housing  8  and a distal housing  9 . In the depicted assembled state of the device  1 , the distal housing  9  is coupled to the proximal housing  8 , for example by a bayonet coupling. 
     The device  1  comprises a dispense member  10  to be operated by a user for dispensing the medicament. In particular, the dispense member  10  is moved in a distal direction, i.e. in a direction defined by a connecting line from the proximal end  6  to the distal end  7 . The movement of the dispense member  10  is accomplished by applying a force, e.g. by the thumb, on a dispense surface of the dispense member  10 , which may correspond to the proximal end  6  of the device  1 . 
     The dispense member  10  is shown in its most proximal position, i.e., a state in which the dispense member  10  protrudes distinctly out of the housing  3 . This indicates to a user that the device has not be used in a dispense operation. 
     The device  1  is operated manually by pushing the dispense member  10  in a distal direction. The dispense member  10  may be pushed into its most distal position until a stop is reached. The movement from the most proximal position to the most distal position corresponds to a full dose dispense operation. The force required for injection may be entirely delivered by a user without support by help mechanisms such as a spring. Also the process of penetration of the needle into the skin may be carried out by direct user force. 
     Accordingly, the device  1  may be a fully manually operated device and not an automatic or a semi-automatic device. In other embodiments the device  1  may be an automatic or a semi-automatic device. As an example, the device  1  may comprises a spring for providing the dispensing force. 
     At its distal end  7 , the device  1  comprises a protective cap  11 , adjacent to the distal housing  9 . The protective cap  11  may be coupled to a needle guard  12 . In the depicted state, the needle guard  12  is concealed by the protective cap  11  and the housing  3  and is indicated with a dashed reference line. The needle guard  12  is explicitly shown in  FIG. 3 , for example. 
     As long as the protective cap  11  is attached, a proximal movement of the needle guard  12  is disabled. In this state, the needle guard  12  is in its most distal position. A proximal movement is a movement in a direction defined by a connecting line from the distal end  7  to the proximal end  6 . In particular, a proximal movement is prevented by abutment of a proximal end of the protective cap  11  on a distal end of the distal housing  9 . 
     In the depicted state of the device  1 , the syringe  2  is fully concealed. Moreover, the dispense member  10  is locked such that a movement of the dispense member  10  relative to the housing  3  is prevented. 
       FIG. 2  shows the assistive device  1  of  FIG. 1  in a pre-assembled state and a syringe  2  to be used with the device  1 . The device  1  and the syringe  1  may be packaged and distributed separately to the user. In another embodiment, the assistive device  1  and the syringe  3  may be provided as a kit such that they are packaged or otherwise distributed together. In both cases, the assistive device  1  may be not yet assembled to each other when being distributed. In other embodiments, the assistive device  1  and the syringe  2  may be in an assembled state when being distributed. 
     The device  1  may be distributed as two pre-assembled parts, a proximal assembly  13  and a distal assembly  14 , not yet attached to each other. 
     The syringe  2  may be a traditional syringe prefilled with a therapeutic agent. The wordings “medicament” and “therapeutic agent” are used as synonyms in this disclosure. 
     For assembling the device  1  and the syringe  2 , the syringe  2  is in a first step accommodated in the distal assembly  14  and, thereafter, the proximal assembly  13  is placed on top over the syringe  2  and aligned with the distal assembly  14 . The proximal assembly  13  is then coupled to the distal assembly  14 , via a bayonet coupling, for example. 
     The proximal assembly  13  comprises the proximal housing  8 , the dispense member  10  and a fixation part  15 . The fixation part  15  is coupled to the proximal housing  8  to prevent a disassembly of the proximal housing  8  and the dispense member  10 . 
     The distal assembly  14  comprises the distal housing  9 , the protective cap  11  and the needle guard  12 . The distal assembly  14  further comprises a needle cap grip  16  which is concealed by the distal housing  9  and is indicated with a dashed reference line. The needle cap grip  16  is explicitly shown in  FIG. 3 , for example. 
     The distal housing  9  comprises a coupling portion  17  comprising a guiding groove  18  for guiding a coupling protrusion  19  of the proximal housing  8  for coupling the proximal assembly  13  to the distal assembly  14 . The coupling protrusion  19  is located at an inner surface of the proximal housing  8  and is indicated by a dashed reference line. The coupling protrusion  19  is explicitly shown in  FIG. 4C , for example. 
     The shape of the guiding groove  17  defines the relative movement of the proximal and distal housings  8 ,  9  during assembly, corresponding to the relative movement of the proximal and distal assemblies  13 ,  14 . In particular, the guiding groove  17  defines a relative axial movement followed by a relative rotational movement of the housing parts  8 ,  9 . A specific embodiment of the coupling portion  17  is described in connection with  FIGS. 6A and 6B . 
     The syringe  2  is also usable as a stand-alone syringe, i.e., without the assistive device  1 . The syringe  2  comprises a barrel  20  containing the medicament. The syringe  2  comprises a needle  21  protected by a needle cap  22 . The position of the needle  21  is indicated by a dashed line. The needle  21  is explicitly shown in  FIG. 9A , for example. 
     A flange  23  is located at a proximal end of the barrel  20 . The flange  23  provides a counter bearing for a user&#39;s fingers when using the syringe  2  without the assistive device  1 . A fitting  24  is connected to the flange  23 , adding surface area and thickness to the flange  23 . The fitting  24  may be removable from the flange  23 . 
     When the syringe  2  is positioned in the distal assembly  14 , the fitting  24  and flange  23  are accommodated in a cradle  25  provided by the distal housing  9 . The outer dimensions of the fitting  24  are matched with the inner dimensions of the cradle  25  such that the fitting  24  accurately fits in the cradle  25 . Accordingly, the fitting  24  adapts the dimensions of the flange  23  to the dimensions of the cradle  25 . Thereby, the position of the syringe  2  in the distal housing  9  is defined and a rotational movement of the syringe  2  relative to the distal housing  9  is disabled. 
     The syringe  2  comprises a plunger  26  being partially accommodated in the barrel  20  and protruding out of a proximal end of the barrel  20 . When the plunger  26  is moved in a distal direction, the medicament is pressed out of the barrel  20  through the needle  21 . A distal end of the plunger  26  may be in direct contact with the medicament or in contact with a piston acting on the medicament. The plunger  26  may be a part belonging intimately to the syringe  2  such that the plunger  26  is unremovably retained in the syringe barrel  20  when distributed to users. Unremovably means that a removal of the plunger is not possible or only possible with great difficulty. 
       FIG. 3  shows an exploded view of the assistive device  1  and a view of the syringe  2 . 
     Regarding the components of the proximal assembly  13 , the dispense member  10  comprises a proximal portion  27  providing a user interface and a distal portion  28  accommodated in the proximal housing  8  in an assembled state of the proximal assembly  13 . The distal portion  28  comprises two flexible arms  29 ,  30 . 
     The flexible arms  29 ,  30  help to define the axial position of the dispense member  10  in the proximal assembly  13  in specific states of the device  1 . In specific embodiments, this may include locking the dispense member  10  in a specific position. The specific states may include one or more of a pre-assembled state, an operational state ready to pierce, an operational state ready to dispense and a state after usage. In particular, the flexible arms  29 ,  30  may provide first locking devices  83 ,  84  for locking the dispense member  10  prior to use and second lock-out devices  106 ,  107  for locking the needle guard  12  after usage. The locking devices  83 ,  84  and lock-out devices  106 ,  107  may overlap with each other. The mechanism of the definition and locking of the axial position is described in detail in connection with the following Figures, e.g. in connection with  FIGS. 9A to 9C . 
     The dispense member  10  comprises a flange  31  located between the proximal portion  27  and the distal portion  28 . When assembling the proximal assembly  13 , the distal portion  28  of the dispense member  10  is positioned in the proximal housing  8 . After that, the fixation part  15  is pushed over the proximal portion  27  of the dispense member  10  until the fixation part  15  engages with the proximal housing  8 . In particular, the fixation part  15  may comprise coupling protrusions (not depicted) at an inner surface engaging in coupling holes  32 ,  33  at the proximal end of the proximal housing  8 . This engagement prevents the proximal assembly  13  from being disassembled after assembly. 
     Regarding the components of the distal assembly  14 , the needle guard  12  has a proximal portion  34 , a middle portion  80  and a distal portion  35 . A flange  36  extends radially outwards and is located between the proximal portion  34  and the middle portion  80 . The proximal portion  34  comprises two racks  37 ,  38 . The racks  37 ,  38  are two portions extending from the flange  36  in a proximal direction. The racks  37 ,  38  may have the shapes of rail-shaped extensions. 
     In specific embodiments, the racks  37 ,  38  interact with the flexible arms  29 ,  30  of the dispense member  10  in order to unlock the dispense member  10  and enable a dispense operation. In this case, the racks  37 ,  38  provide release devices  102 ,  103 . Additionally or alternatively, the racks  37 ,  38  may be involved in locking the needle guard  12  after use. In this case, the racks  37 ,  38  provide first lock-out devices  104 ,  105 . 
     The distal housing  9  comprises two lead-throughs  39 ,  40  for accommodating the racks  37 ,  38  and allowing a movement of the needle guard  12  in a proximal direction for exposing the needle. The lead-throughs  39 ,  40  are open toward a proximal and distal direction such that the racks  37 ,  38  are enabled to protrude out of the lead-throughs  39 ,  40  in both directions. 
     The distal housing  9  comprises a shoulder  41  and openings  42 ,  43  above the shoulder  41  for accommodating retention protrusions  44 ,  45  of the needle guard  12 . The retention protrusions  44 ,  45  cooperate with the shoulder  41  to prevent the needle guard  12  from slipping out of the distal end of the distal housing  9 . 
     Furthermore, an inner face at the shoulder  41  interacts with the flange  36  of the needle guard  12 , when the needle guard  12  is moved in a proximal direction for exposing the needle  21  and, thus, limits movement of the needle guard  12  in the proximal direction. 
     As can be further seen, the cap grip  16  has the shape of a ring. When forming the distal assembly  14 , the cap grip  16  is fixed to the protective cap  11 , by a snap-in connection, for example. The cap grip  16  serves to grip the needle cap  22  when the syringe  2  is placed in the distal assembly  14 . When the protective cap  11  is removed, the protective cap  11  together with the cap grip  16  pulls the needle cap  22  off the syringe  2  and exposes the needle  21 . A specific embodiment of the cap grip  16  is described in connection with  FIG. 7D . 
     For assembling the distal assembly  14 , the cap grip  16  is fixed to the protective cap  11  and then the protective cap  11  is attached to the distal portion  35  of the needle guard  12 . After that, the needle guard  12  is pushed through the distal end of the distal housing  9  in the proximal direction, until the retention protrusions  44 ,  45  protrude out of the openings  42 ,  43  and are located directly above the shoulder  41 . In this position, a proximal surface of the protective cap  11  abuts a distal surface of the distal housing  9  such that the components of the distal assembly  14  are locked in their positions. In particular, any movement of the needle guard  12  relative to the distal housing  9  is disabled. 
     In the assembled state, the components of the proximal assembly  13  are locked such that relative movements of the components are prevented in the proximal assembly  13 . Additionally, the components of the distal assembly  14  are locked such that relative movements of the components are prevented in the distal assembly  14 . This simplifies the handling of the device  1 , in particular the assembly of the proximal assembly  13  with the syringe  2  and with the distal assembly  14 , because no movable components are involved. 
       FIGS. 4A to 4C  show the proximal assembly  13  in a side view, in a top view and in a longitudinal-sectional view, respectively. The line of intersection for the longitudinal sectional view is indicated in  FIG. 4B  by a line marked with “ 4 C- 4 C”. 
     As can be seen in  FIG. 4C , the proximal housing  8  has an inner surface  46  and retention protrusions  47 ,  48  protruding from the inner surface  46 . The retention protrusions  47 ,  48  serve as an abutment face for distal end faces of the flexible arms  29 ,  30  of the dispense member  10  during formation of the proximal assembly  13  and limit how far the dispense member  10  can be pushed in a distal direction. 
     The retention protrusions  47 ,  48  serve as second locking devices  85 ,  86  for interaction with the first locking devices  83 ,  84  of the dispense member  10 , to lock the dispense member  10  to the proximal housing  8 . In particular, the interaction of the retention protrusions  47 ,  48  with the flexible arms  29 ,  30  prevent a distal movement of the dispense member  10  relative to the proximal housing  8 , both before and after coupling of the proximal assembly  13  with the distal assembly  14 . 
     In addition to that, a movement of the dispense member  10  in the proximal direction is prevented by an interaction of the flange  31  of the dispense member  10  with the fixation part  15 . 
     The proximal housing  8  further comprises an annular retention ledge  49  defining first and second armholes  50 ,  51 . The armholes  50 ,  51  are positioned on opposite sides of the proximal housing  8 . Both armholes  50 ,  51  extend parallel to the centerline  5  and are open to both a proximal face and a distal face of the annular retention ledge  49 . The retention protrusions  47 ,  48  are positioned in the first and second armholes  50 ,  51 , respectively. The retention protrusions  47 ,  48  do not extend all the way across the armholes  50 ,  51  but leave a gap of sufficient width to allow the flexible arms  29 ,  30  of the dispense member  10  to pass through the armholes  50 ,  51  during a dispense operation, as described in detail in connection with  FIG. 9B , for example. 
       FIG. 4C  also shows the coupling protrusion  19  that interacts with the coupling portion  17  of the distal housing  9  and is guided in the guiding groove  18  for coupling the proximal housing assembly  13  to the distal housing assembly  14 . The coupling protrusion  19  projects from the inner surface  46  of the proximal housing  8  and is positioned between the retention ledge  49  and the distal end of the proximal housing  8 . 
     The dispense member  10  comprises a post  52 , in particular a tubular post, extending from the proximal end  6  of the dispense member  10  in the distal direction. The post  52  directly interacts with the plunger  26  of the syringe  2  to push the plunger  26  in a distal direction during a dose dispense operation. Accordingly, the post  52  directly transmits the pushing force exerted by a user on the dispense surface to the plunger  26 . 
       FIGS. 5A to 5C  show the dispense member  10  in a side view, a side view rotated by an angle of 90° compared to  FIG. 5A  and a longitudinal-sectional view, respectively. 
     As can be seen in  FIGS. 5A and 5C , the post  52  protrudes out of the proximal portion  27 . 
     The first and second flexible arms  29 ,  30  are positioned on opposite sides of the dispense member  10  and extend from the distal end of the proximal portion  27  in a distal direction. 
     The flexible arms  29 ,  30  are flared such that the distance between each flexible arm  29 ,  30  and the centerline  5  increases in the distal direction. The flexible arms  29 ,  30  are resilient. When tips  53 ,  54  of the flexible arms  29 ,  30 , i.e., the distal ends of the flexible arms  29 ,  30 , are pressed towards the centerline  5 , a resilient counterforce is provided by the flexible arms  29 ,  30 . 
     When the flexible arms  29 ,  30  are positioned in the proximal housing  8  after forming the proximal assembly  13  and before using the device  1 , the tips  53 ,  54  are pressed slightly towards the centerline  5  by an inner surface  46  of the proximal housing  8  such that the flexible arms  29 ,  30  are resiliently biased and a counterforce is exerted by the tips  53 ,  54  on the inner surface  46 . This resilient force prevents the flexible arms  29 ,  30  from moving towards the centerline  5  and from disengaging from the retention protrusions  47 ,  48 . Accordingly, the flexible arms  29 ,  30  serve as first locking devices  83 ,  84  for locking the dispense member  10  before proximal movement of the needle guard  12 . 
     As can be seen in  FIG. 5B , the tip  53  of the flexible arm  29  has beveled surfaces  55 ,  56 . The beveled surfaces  55 ,  56  face the inner surface  46  of the proximal housing  8 . Between the beveled surfaces  55 ,  56  of the tip  53 , a protruding portion  57  is located, the protruding portions  57  having a thickness larger than the ends of the beveled surfaces  55 ,  56 . Due to the larger thickness, the protruding portion  57  abuts on the inner surface  46  such that a gap is provided between the beveled surfaces  55 ,  56  and the inner surface  46 . The beveled surfaces  55 ,  56  and the protruding portion  57  interacts with the rack  37  of the needle guard  12  for unlocking the dispense member  10  to enable a movement in a distal direction. The second flexible arm  30  has a corresponding shape and a corresponding interaction of a protruding portion  58  with the second rack  38 . The details of the mechanism are described in connection with  FIG. 9B , for example. 
     As can be further seen in  FIGS. 5A to 5C , each of the flexible arms  29 ,  30  has an opening  59 ,  60  near the distal end. These openings  59 ,  60  serve as first lock-out devices  104 ,  105  for locking the dispense member  10  with the needle guard  12  after a dispense operation, as is described in connection with  FIG. 9C , for example. 
       FIGS. 6A to 6E  show the distal housing  9  in a perspective view, a side view, a rotated side view, a top view and a longitudinal-sectional view, respectively. The line of intersection for the longitudinal-sectional view is indicated in  FIG. 6D  by a line marked with “ 6 E- 6 E”. 
     The distal housing  9  has a proximal portion  61  and a distal portion  62 . The perimeter of the distal portion  62  is larger than the perimeter of the proximal portion  61 . The shoulder  41 , which prevents slipping of the needle guard  12  out of the distal housing  9 , is formed between the proximal portion  61  and the distal portion  62 . The distal portion  62  has an outer perimeter that has the same shape and size as the outer perimeter of the proximal housing  8 . The outer perimeter of the proximal portion  61  has the same shape, but is slightly smaller than the inner surface  46  of the proximal housing  8  such that, in an assembled state, the proximal portion  61  is accommodated in the proximal housing  8 . 
     In the following, a specific embodiment of the coupling mechanism for coupling the proximal assembly  13  to the distal assembly  14  is described in connection with  FIGS. 6A and 6B . In other embodiments, the coupling mechanism may be different. 
     The coupling portion  17  comprises the guiding groove  18  that forms a track for guiding the coupling protrusion  19  of the proximal housing  8 . The guiding groove  18  has a first portion  63  that receives the coupling protrusion  19  and is open towards the proximal edge of the distal housing  9 . The first portion  63  has a larger width at its proximal end in order to facilitate leading the coupling protrusion  19  in the groove  18 . 
     The groove  18  has a second portion  64  that is at an angle from the first portion  63 . An end  65  of the groove  18  is closed and forms a hard stop for the coupling protrusion  19  and hence stops rotation of the proximal housing  8  relative to the distal housing  9 . 
     A snap hole  66  is formed through the wall of the distal housing  9  and extends from the surface of the groove  18  to the inner surface of the distal housing  9 . A latch  67  is located at the wall of the distal housing  9  and extends into the snap hole  66 . The latch  67  is resilient and can flex into the inner volume of the distal housing  9  toward the centerline  5 . The end portion of the latch  67  has a retention surface  68  that ramps radially outward away from the centerline  5  and toward the outer perimeter of the distal housing  9 . 
     When the proximal assembly  13  and the distal assembly  14  are connected to place the device  1  into an operational state, the coupling protrusion  19  is positioned into and moved through the groove  18  until it engages and moves over the retention surface  68 . As the coupling protrusion  19  moves over the retention surface  68 , the latch  67  flexes and moves toward the inner chamber of the distal housing  9 . When the coupling protrusion  19  passes the retention surface  68 , the flange  67  snaps, or otherwise returns to its resting position and the coupling protrusion  19  is held securely between the retention surface  68  and the end  65  defining a hard stop surface of the groove  18 . 
     The snapping action of the latch  67  when the coupling protrusion  19  moves over the retention surface  68  may provide confirmation to a user that the proximal assembly  13  has been successfully attached to the distal assembly  14  such that the device  1  is in an operational state. 
     The retention surface  68  may have an increased thickness near the center of the retention surface  68  such that the retention surface  68  ramps up and down so that the coupling protrusion  19  may be enabled to move over the retention surface  68  in both directions, enabling a user to both attach and detach the proximal assembly  13  to and from the distal assembly  14 . According to a different embodiment, the coupling mechanism may be configured such that a detachment of the proximal assembly  13  from the distal assembly  14  is disabled. 
     As can be also seen in  FIGS. 6A to 6E , the cradle  25  is formed by a shallow wall that projects up at a proximal end of the distal housing  9 . The perimeter of the shallow wall has a shape and size similar to the shape and size of the fitting  24  on the syringe flange  23 . When the syringe  2  is inserted into the distal assembly  9 , the syringe fitting  24  and flange  23  fit within the cradle  25 . When the proximal assembly  13  is connected to the distal assembly  14  the depth of the space between the proximal surface of the distal housing  9  and the distal surface of the annular retention ledge  49  in the proximal housing  8  is slightly smaller than the thickness of the syringe fitting  24 . Thereby, the syringe fitting  24  and flange  23  are pinched between the proximal housing  8  and distal housing  9  and cannot move axially in an assembled state of the device  1 . The cradle  25  also prevents the syringe  12  from rotating. 
     As can best be seen in  FIG. 6E , the cradle  25  has an opening  69  in its bottom surface leading to a tubular post  70  in which the syringe barrel  20  is accommodated and confined in its position relative to the distal housing  9 . The tubular post  70  has a smaller outer perimeter than the perimeter of an inner surface  71  of an outer wall of the distal housing  9 . The gap between the tubular post  70  and the inner surface  71  define the lead-throughs  39 ,  40  accommodating the racks  37 ,  38  of the needle guard  12 . 
       FIGS. 7A to 7E  show the needle guard  12  in a perspective view, a side view, a rotated side view, a top view and a longitudinal-sectional view, respectively. The line of intersection for the longitudinal-sectional view is indicated in  FIG. 7D  by a line marked with “ 7 E- 7 E”. 
     The two racks  37 ,  38  are located on opposite sides of the needle guard  12  in the proximal portion  34  of the needle guard  12 . The racks  37 ,  38  extend parallel to the centerline  5 . The racks  37 ,  38  are rigid, i.e. non-flexible. The proximal edge of each rack  37 ,  38  defines a slot  72 ,  73  open to the proximal edge. The slots  72 ,  73  receive the retention protrusions  47 ,  48  at the inner surface  46  of the proximal housing  8  when releasing the locking of the dispense member  10 . 
     The slot  72  is confined by two proximal tip portions  74 ,  75 , each tip portion  74 ,  75  having a beveled surface  76 ,  77  at an inwardly facing surface of the needle guard  12 . The beveled surfaces  76 ,  77  are sized, shape and arranged to slide in between the beveled surfaces  55 ,  56  of the tip  53  of the flexible arm  29  of the dispense member (see  FIG. 5B ) and the inner surface  46  of the proximal housing  8  when the needle guard  12  moves in a proximal direction to unlock the dispense member  10 . The second rack  38  has a corresponding interaction with the second flexible arm  30 . 
     As explained above, the needle guard  12  has retention protrusions  44 ,  45  interacting with the shoulder  41  in the proximal housing  9  to prevent slipping of the needle guard  12  out of the housing  9 . Furthermore, the flange  36  has an outer perimeter smaller than the perimeter of the inner surface of the distal portion  62  of the distal housing  9  and is larger than the perimeter of the inner surface of the proximal portion  61  of the distal housing  9 . This enables the needle guard  12  to move along the centerline  5  in the distal portion  61  of the distal housing  9  until the flange  36  abuts a part of an inner wall at the shoulder  41 . 
     At the bottom edge of the distal portion  35 , the needle guard  12  has a cap retention flange  78  extending radially outwards. The flange  78  serves to hold the protective cap  11  in place when the protective cap  11  is attached to the distal assembly  14  prior to use. 
     The needle guard  12  further has an annular flange  79  between the distal portion  35  and the middle portion  80 . The annular flange  79  has an outer perimeter adapted to the perimeter of an inner surface of the distal housing  9  such that the needle guard  12  is securely guided along the inner surface of the distal housing  9 . 
     As can be seen in  FIG. 7D , the needle guard  12  defines a center channel  81  extending all the way through the needle guard  12 . The center channel  81  has a perimeter larger than the outer perimeter of the syringe barrel  20 . A plurality of projections  82  extend in the center channel  81  towards the centerline  5 . Each of the projections  82  has a tip, and the tips of the projections  82  define a cross-sectional area that is orthogonal to the centerline  5  and that has a perimeter slightly smaller than the outer diameter of the syringe barrel  20 . When placing the syringe  2  in the distal assembly  14 , the barrel  20  engages the projections  82  as it passes through the center channel  81 . The projections  82  center the barrel  20  and provide a slight amount of friction between the projections  82  and the barrel  20 . Thereby, the projections  82  prevent the barrel  20  of the syringe  2  from moving laterally to the centerline  5  and still permit the needle shroud  12  to slide proximally along the length of the barrel  20 . 
     As can be seen in the longitudinal-sectional view shown in  FIG. 7E , the needle guard  12  comprises first lock-out devices  104 ,  105  located at a distal portion of the racks  37 ,  38 . The lock-out devices  104 ,  105  interact with the second lock-out devices  106 ,  107  of the dispense member  10  to lock the needle guard  12  with the dispense member  10  after the full dose of medicament has been dispensed. Thereby, any relative movements of the dispense member  10  and the needle guard  12  are prevented. The locking is permanent and, thus, cannot be released by a user. 
     The first lock-out devices  104 ,  105  comprise lock-out protrusions  87 ,  88  protruding inwardly from an inner wall of the needle guard  12 . In addition to that, the first lock-out devices  104 ,  105  comprise lock-out openings  89 ,  90  leading through an inner wall of the needle guard  12 . The lock-out protrusions  87 ,  88  are sized to fit into the first and second armholes  50 ,  51  at the distal ends of the flexible arms  29 ,  30  of the dispense member  10 . The lock-out protrusions  87 ,  88  comprise ramped upper surfaces  91 ,  92  for pressing the tips  53 ,  54  of the flexible arms  29 ,  30  inwardly when the needle guard  12  moves in a distal direction and when the beveled surfaces  55 ,  56  of the tips  53 ,  54  slide along the ramped upper surfaces  91 ,  92 . 
     In an alternative embodiment, lock-out may be provided entirely by a friction force between the flexible arms  29 ,  30  and the racks  37 ,  38 . In this case, the lock-out openings  89 ,  90  and lock-out protrusions  87 ,  88  may not be present. 
       FIGS. 8A to 8D  show the protective cap  11  in a perspective view, a side view, a top view and a longitudinal-sectional view, respectively. The line of intersection for the longitudinal-sectional view is indicated in  FIG. 8C  by a line marked with “ 8 D- 8 D”. 
     The protective cap  11  has a proximal end  93  and a distal end  7 , and defines an inner volume  94 . The proximal end  93  is open and sized to receive the distal portion  35  of the needle guard  12 . The distal end  7  is closed and has a bottom wall  96  that is orthogonal to the centerline  5 . A plurality of retention members  96  is positioned in the inner volume  94  and extend upwards from the bottom wall  96 . Near the proximal ends of the retention members  96  cap retention ridges  97  extend inwards toward the centerline  5 . The radial distance from the centerline  5  to each of the cap retention ridges  97  is slightly smaller than the radius of the cap retention flange  78  of the needle guard  12 . Thus, when the device  1  is in its assembled pre-use configuration, the cap retentions ridges  97  snap over the cap retention flange  78  and hold the protective cap  11  in place on the distal portion  35  of the needle guard  12 . 
     The protective cap  11  can be removed from the needle guard  12  by pulling the protective cap  11  in a distal direction so that the cap retention ridges  97  snap over the cap retention flange  78 . The cap retention ridges  97  are formed with a resilient material that enables them to flex at least slightly to provide the snap mechanism allowing the protective cap  11  to be attached to and removed from the needle guard  12 . 
     A tubular post  98  extends upwards from the bottom of the protective cap  11  and into the inner volume  94 . The tubular post  98  is open at its proximal end. The tubular post  98  defines a volume  99  sized to receive the needle cap  22 . The needle cap grip  16  is attached to the tubular post  98 . The needle cap grip  16  and the tubular post  98  are concentric. The tubular post  98  has an inner diameter that is larger than the needle cap  22 . A plurality of teeth  100  extend from the inner edge of the needle cap grip  16 , and have an end portion. The radial position between the centerline  5  and the end portion of the teeth  100  is smaller than the outer diameter of the needle cap  22 . When the syringe  2  is inserted into the distal assembly  14 , the teeth  100  securely grip the needle cap  22 . When the protective cap  11  is removed from the needle guard  12 , the protective cap  11  and needle cap grip  16  pull the needle cap  22  off the syringe  2  and expose the needle  21 . 
     The operation of the assistive device  1  comprising the syringe  2  is described now in detail in connection with  FIGS. 9A, 9B and 9C . 
     The assistive device  1  and therewith, the medication delivery device  4 , has several states. These states may all occur after distribution to a user. 
     A first state is the pre-assembled state as shown in  FIG. 2 . In the pre-assembled state, the proximal assembly  13 , the distal assembly  14  and the syringe  2  are not yet assembled with each other. 
     A further state is an operational state, in which the device  1  is assembled with the syringe  2  and wherein a dispense operation has not started or a dose has not been fully dispensed. The operational state is depicted in  FIGS. 9A and 9B , wherein  FIG. 9A  shows the device  1  before exposing the needle  21  and  FIG. 9B  shows the device  1  after exposing the needle  21  and before dispensing the medicament. 
     A further state is a locked-out state, in which the dispense member  10  has been fully depressed such that the dose has been fully dispensed and the device  1  is locked-out to prevent a re-use of the device  1 . The locked-out state is shown in  FIG. 9C . 
     Returning to the pre-assembled state as shown in  FIG. 2 , a user assembles the components by placing the syringe  2  in the distal assembly  14 . In particular, the syringe  2  is inserted into the opening  69  (see  FIG. 6D ) of the distal housing  9  and the center channel  81  (see  FIG. 7D ) of the needle guard  12  until the syringe flange  23  and the syringe fitting  24  are seated in the cradle  25  and rest against the proximal surface of the distal housing  9 . In this position, the needle cap  22  is inserted into the needle cap grip  16  in the protective cap  11  so that the teeth  100  grip the outer surface of the needle cap  22 . 
     The user then attaches the proximal assembly  13  to the distal assembly  14  to place the device  1  in the assembled state. To attach the assemblies  13 ,  14 , the user inserts the coupling protrusion  19  all the way through the first portion  63  of the guiding groove  18 . In this position, the plunger  26  of the syringe  2  is positioned in the dispense member  10 . The user then twists the proximal assembly  13  relative to the distal assembly  14  so that the coupling protrusion  19  travels through the second portion  64  of the guiding groove  18  and clicks over the retention surface  68  of the latch  67 . 
     The device  1  is now in the operational state and ready to use. However, as long as the protective cap  11  is attached, a movement of the needle guard  12 , and thereby also of the dispense member  10  is prevented. In particular, the proximal end  93  of the protective cap  11  abuts a distal end of the distal housing  9  and, thereby, blocks the protective cap  11  and the needle guard  12  from moving in a proximal direction. 
     Furthermore, the dispense member  10  is locked in its position due to the interaction of the first locking devices  83 ,  84 , in particular the tips  53 ,  54  of the flexible arms  29 ,  30 , with the second locking devices  85 ,  86 , in particular, the retention protrusions  47 ,  48 . 
     To start an operation, the user pulls the protective cap  11  off the distal portion  35  of the needle guard  12 . 
       FIG. 9A  shows the device  1  in the state after removal of the protective cap  11  and, thereby, also of the needle cap  22 . The tip of the needle  21  is covered by the distal portion  35  of the needle guard  12  and is not exposed. This state is an operational state ready to pierce a skin by the needle  21 . The needle guard  12  is movable in a proximal direction. 
     In this state, the dispense member  10  is still locked, i.e. unable to move in a distal direction. The tubular post  52  of the dispense member  10  is located above the plunger  26 . A gap may exist between the tubular post  52  and the plunger  26 . 
     In a second step of operation, the needle guard  12  is moved in a proximal direction and the device  1  is thereby brought in an operational state ready to dispense the medicament as shown in  FIG. 9B . This means that the movement of the dispense member  10  is now enabled without that any further unlocking action is required. 
     In particular, starting from the state shown in  FIG. 9A , the user presses a distal surface  101  of the needle guard  12  against his/her skin at the injection site and presses the device  1 , in particular the assembled housings  8 ,  9  towards the skin. As the housings  8 ,  9  move towards the skin, the needle guard  12  is pushed in a proximal direction relative to the housings  8 ,  9 . The distal portion  35  of the needle guard  12  slides into the distal housing  9  until the flange  36  of the needle guard  12  abuts with a distal surface at the shoulder  41 . The distal surface  101  of the needle guard  12  may now be flush with the distal end of the distal housing  9 . The needle  21  is exposed and pierces the skin. 
     As the needle guard  12  moves in the proximal direction, the racks  37 ,  38  slide through the lead-throughs  39 ,  40  further in the proximal housing  8 . The beveled surfaces  76 ,  77  of the tip  74 ,  75  of the rack  37  slide on the beveled surfaces  55 ,  56  of the tip  53  of the flexible arm  29 . Corresponding interactions occur between the second rack  38  and second flexible arm  30 . In this action, the first and second racks  37 ,  38  slide between the first and second flexible arms  29 ,  30  of the dispense member  10  and the inner surface  46  of the proximal housing  8 . Thereby, the tips  53 ,  54  of the flexible arms  29 ,  30  are moved inwardly and are separated from the inner surface  46  of the proximal housing  8 . The tips  53 ,  54  are in a radial position inwardly from the retention protrusions  47 ,  48  and, thus, off from the retention protrusions  47 ,  48 . 
     The tip portions  74 ,  75  of the rack  37  that defines the slot  72  move along either side of the retention protrusion  47  so that the retention protrusion  47  is now positioned in the slots  72  of the rack  37  respectively. Corresponding interactions occur between the second rack  38  and second retention protrusion  48 . The dispense member  10  is now free to move and to be depressed into the proximal housing  8 . Accordingly, the racks  37 ,  38  provide release devices  102 ,  103  for releasing the locking of the dispense member  10  with the proximal housing  8 . 
     In a third step of operation, the medicament is dispensed by moving the dispense member  10  in the distal direction. When the dispense member  10  is fully depressed, the device  1  acquires a locked-out state as shown in  FIG. 9C . 
     To inject medication, the dispense member  10  is moved in a distal direction, e.g., by placing the thumb on the proximal end  6  of the dispense member and pushing downwards. As the dispense member  10  is depressed, it moves through the proximal housing  8  and presses the syringe plunger  26  into the barrel  20 . Accordingly, the dispense member  10  directly acts on the plunger  26 . Thus, the dispense member  10  and the plunger  26  carry out identical movements during dispense of the medication. The plunger  26  moves forwards in the barrel  20  and pushes the medicament out of the needle  21 . 
     As the dispense member  10  moves, the first and second flexible arms  29 ,  30  slide along the surfaces of the racks  37 ,  38 , respectively. The flexible arms  29 ,  30  are pretensioned and provide a resilient force on the racks  37 ,  38 . Due to the resilient force, the dispense member  10  remains in its axial position when inadvertently released during a dose dispense operation. 
     At the end of the dispense operation, the first lock-out devices  104 ,  105  of the needle guard  12  interlock with the second lock-out devices  106 ,  107  of the dispense member  10 . In particular, the beveled surfaces  55 ,  56  of the tip  53  of the flexible arm  29  slide along ramped upper surfaces of the lock-out protrusion  87  of the needle guard  12 . Corresponding interactions occur between the second flexible arm  30  and second lock-out protrusion  88 . Thereby, the tips  53 ,  54  of the flexible arms  29 ,  30  move inwardly, pass the lock-out protrusions  87 ,  88  and snap outwards under the lock-out protrusions  87 ,  88 . The lock-out protrusions  87 ,  88  are now located in the openings  59 ,  60  in the distal portions of the flexible arms  29 ,  30 . 
     This action interlocks the dispense member  10  and the needle guard  12  and holds them in their used final positions. In particular, the dispense member  10  can no longer slide proximally back out of the proximal housing  8  and the needle guard  12  can no longer distally slide out of the distal housing  9 . Accordingly, the dispense member  10  remains permanently in a fully depressed position and the needle guard  12  remains permanently in a fully retracted position. Thus, also the needle  21  remains permanently exposed after usage. This clearly signals to a user that the device  1  has been used for dispensing the medicament and should be discarded. 
     In an alternative embodiment, the lock-out mechanism is provided by the friction force between the flexible arms  29 ,  30  and the racks  37 ,  38 . When the dispense member  10  is fully depressed, a manual extension of the dispense member  10  or the needle guard  12  may be impractical for a user. The same applies to a manual extension of the needle guard  12 . 
     The interlocking of the dispense member  10  and the needle guard  25  also keeps the proximal assembly  13  and the distal assembly  14  from being detached and prevents the syringe  2  from being removed from the device  1  and being used again. This may increase the safety of the device  1 . 
     REFERENCE NUMERALS 
     
         
           1  assistive device 
           2  syringe 
           3  housing 
           4  medication delivery device 
           5  centerline 
           6  proximal end 
           7  distal end 
           8  proximal housing 
           9  distal housing 
           10  dispense member 
           11  protective cap 
           12  needle guard 
           13  proximal assembly 
           14  distal assembly 
           15  fixation part 
           16  cap grip 
           17  coupling portion 
           18  guiding groove 
           19  coupling protrusion 
           20  barrel 
           21  needle 
           22  needle cap 
           23  flange of syringe 
           24  fitting 
           25  cradle 
           26  plunger 
           27  proximal portion of dispense member 
           28  distal portion of dispense member 
           29  first flexible arm 
           30  second flexible arm 
           31  flange of dispense member 
           32  first coupling hole 
           33  second coupling hole 
           34  proximal portion of needle guard 
           35  distal portion of needle guard 
           36  flange of needle guard 
           37  first rack 
           38  second rack 
           39  first lead-through 
           40  second lead-through 
           41  shoulder 
           42  first opening 
           43  second opening 
           44  first retention protrusion 
           45  second retention protrusion 
           46  inner surface of proximal housing 
           47  first retention protrusion 
           48  second retention protrusion 
           49  annular retention ledge 
           50  first armhole 
           51  second armhole 
           52  tubular post 
           53  first tip 
           54  second tip 
           55  first beveled surface of flexible arm 
           56  second beveled surface of flexible arm 
           57  protruding portion 
           58  protruding portion 
           59  first opening 
           60  second opening 
           61  proximal portion of distal housing 
           62  distal portion of distal housing 
           63  first portion of groove 
           64  second portion of groove 
           65  end of groove 
           66  snap hole 
           67  latch 
           68  retention surface 
           69  opening 
           70  tubular post of distal housing 
           71  inner surface of outer wall of distal housing 
           72  slot 
           73  slot 
           74  first tip portion 
           75  second tip portion 
           76  first beveled surface 
           77  second beveled surface 
           78  cap retention flange of needle guard 
           79  annular flange of needle guard 
           80  middle portion of needle guard 
           81  center channel 
           82  plurality of projections 
           83  first locking device of dispense member 
           84  first locking device of dispense member 
           85  second locking device of housing 
           86  second locking device of housing 
           87  lock-out protrusion 
           88  lock-out protrusion 
           89  lock-out opening 
           90  lock-out opening 
           91  ramped upper surface 
           92  ramped upper surface 
           93  proximal end of protective cap 
           94  inner volume 
           95  bottom wall 
           96  retention members 
           97  cap retention ridges 
           98  tubular post of protective cap 
           99  inner volume of tubular post 
           100  plurality of teeth 
           101  distal surface of needle guard  12   
           102  first release device 
           103  second release device 
           104  first lock-out device of needle guard 
           105  first lock-out device of needle guard 
           106  second lock-out device of dispense member 
           107  second lock-out device of dispense member