Abstract:
The present invention is directed to an automatic injection device containing a pre-loaded charge of medicament for automatically self-administering the medicament upon actuation thereof. The present invention is directed to an automatic injection device containing a pre-loaded charge of medicament for automatically self-administering the medicament upon actuation thereof. The injection device includes a housing assembly, a dry compartment located within the housing for storing a predetermined dry charge of dry medicament therein, and a wet compartment located within the housing for storing a predetermined amount of liquid injection solution therein. The injection device further includes an activation assembly that enables the pressurization of the liquid injection solution in the wet compartment. The activation assembly also enables the compression of the dry medicament within the dry compartment upon activation of the automatic injection device. The activation assembly further facilitates passage of the liquid injection solution from the wet compartment to the dry compartment upon activation of the automatic injection device.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims priority from U.S. provisional Ser. No. 60/238,447, filed Oct. 10, 2000, and is incorporated herein in its entirety by reference 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to automatic injectors for delivering medicament to an injection site. In particular, the present invention is directed to an automatic injector assembly for quickly combining a liquid material with a dry material to form a liquid medicament for delivering the medicament to an injection site. In accordance with the present invention, the automatic injector assembly includes a pair of movable plunger assemblies within the injector assembly for pressurizing the liquid injection solution and compressing the dry medicament.  
         BACKGROUND OF THE INVENTION  
         [0003]    An automatic injector is a device for enabling an individual to self-administer a dosage of medicament into his or her flesh. The medicament is usually stored in liquid form. The advantage of automatic injectors is that they contain a measured dosage of a liquid medicament in a sealed sterile cartridge and can be utilized for delivering the medicament into the flesh during emergency situations. Another advantage of automatic injectors is that the self-administration of the medicament is accomplished without the user initially seeing the hypodermic needle through which the medicament is delivered and without having the user to manually force the needle into his or her own flesh.  
           [0004]    There are drawbacks associated with the storage of medicament in liquid form. Some medicaments are not stable in liquid form. Furthermore, some liquid medicaments typically have a shorter shelf life than their solid counterparts. Others have developed automatic injectors that store the medicament in solid form and a liquid injection solution. These injectors, disclosed for example in U.S. Reissue Pat. No. 35,986, entitled “Multiple Chamber Automatic Injector,” (the disclosure of which is incorporated herein specifically by reference), however, require the user of the injector to expedite dissolution of the solid component by manually shaking the liquid component and the solid component immediately prior to injection. This increases the time needed to administer a dose of medicament. Furthermore, the improper mixing of the medicament with the liquid injection solution may release an insufficient dose of medicament. There is a need for an automatic injector that stores medicament in solid form that does not require manual premixing by the user. Furthermore, rapid delivery of the medicament is needed for emergency medical situations (e.g. nerve gas and chemical agent poisoning).  
         OBJECTS OF THE INVENTION  
         [0005]    It is therefore an object of the present invention to provide an automatic injector device that stores medicament in a solid form for increased shelf life.  
           [0006]    It is another object of the present invention to provide an automatic injector device that automatically mixes a solid medicament with a liquid injection solution upon activation.  
           [0007]    It is another object of the present invention to provide an automatic injector device that pressurizes a stored liquid injection solution upon activation of the automatic injector device.  
           [0008]    It is another object of the present invention to provide an automatic injector device that compresses the dry medicament upon pressurization of the stored liquid injection solution.  
           [0009]    It is another object of the present invention to provide an automatic injector device that minimizes residual space within the injector device to limit the trapping of dry medicament.  
           [0010]    It is another object of the present invention to provide an automatic injector device that permits the injection of a medicament without the need for shaking the automatic injector device.  
           [0011]    Additional objects and advantages of the invention are set forth, in part, in the description which follows, and, in part, will be apparent to one of ordinary skill in the art from the description and/or practice of the invention.  
         SUMMARY OF THE INVENTION  
         [0012]    In response to the foregoing challenges, applicants have developed an innovative automatic injection device having both wet and dry storage compartments. The present invention is directed to an automatic injection device containing a pre-loaded charge of medicament for automatically self-administering the medicament upon actuation thereof. The present invention is directed to an automatic injection device containing a pre-loaded charge of medicament for automatically self-administering the medicament upon actuation thereof. The injection device includes a housing assembly, a dry compartment located within the housing for storing a predetermined dry charge of dry medicament therein, and a wet compartment located within the housing for storing a predetermined amount of liquid injection solution therein. The injection device further includes an activation assembly that enables the pressurization of the liquid injection solution in the wet compartment. The activation assembly also enables the compression of the dry medicament within the dry compartment upon activation of the automatic injection device. The compression of the medicament occurs independently of the application of pressure on the liquid injection solution. The activation assembly further facilitates passage of the liquid injection solution from the wet compartment to the dry compartment upon activation of the automatic injection device. The injection device also includes a needle assembly for dispensing the liquid injection solution containing the medicament dissolved therein.  
           [0013]    In accordance with present invention, it is contemplated that the activation assembly may include a first pressure element that applies pressure to the liquid injection solution within the wet compartment upon activation of the automatic injection device. The activation assembly may further include a second pressure element that compresses the dry medicament within the dry compartment upon activation of the automatic injection device. The second pressure element provides a barrier between the wet compartment and the dry compartment to prevent the transfer of the liquid injection solution from the wet compartment to the dry compartment prior to activation of the automatic injection device.  
           [0014]    The activation assembly may further include a linking member for transmitting a force from the first pressure element and the collet to the second pressure element to facilitate compression of the dry medicament. It is contemplated that the first pressure element frictionally engages the linking element to apply a force from the first pressure element to the linking element. The application of pressure on the second pressure element through the linking element occurs such that the dry medicament may be compressed prior to the pressurization of the liquid injection solution. The linking element is slidably received within an aperture within the first pressure element. The linking member is adapted to come in or be in contact with the second pressure element. The linking element may include a stepped surface or have a slight change in diameter on the shaft of the linking member such that the first pressure element contacts the stepped surface/change in diameter to initially drive the second pressure element, which ensures pressure on the dry medicament. The force of the spring assembly may be sufficient to overcome the forces associated with the diameter change of the linking element, whereby the first pressure element slides along the linking element to pressurize the liquid injection solution and force the solution into the dry compartment.  
           [0015]    The present invention is also directed to a method of mixing a dry medicament with a liquid injection solution in an automatic injection device for administering a dosage of medicament to a user. The automatic injection device includes a dry compartment for storing the dry medicament prior to mixing, a wet compartment for storing a supply of liquid injection solution prior to mixing, and a needle assembly for transferring a mixture of dissolved dry medicament and the liquid injection solution to a user. The method includes activating the automatic injection device, pressurizing the liquid injection solution in the wet compartment and simultaneously compressing the dry medicament in the dry compartment. The method further includes opening a fluid path between the wet compartment and the dry compartment to permit the passage of the liquid injection solution from the wet compartment to the dry compartment, dissolving the dry medicament in the liquid injection solution within the dry compartment, and transferring the mixture of the dissolved dry medicament and the liquid injection solution through the needle assembly to the user.  
           [0016]    In accordance with the present invention, the pressurization of the liquid injection solution in the wet compartment may include applying a force on a first pressure element within the wet compartment. The compression of the dry medicament in the dry compartment may include transferring a force from the first pressure element to a second pressure element, and compressing the dry medicament with the second pressure element. The opening of the fluid path between the wet compartment and the dry compartment may include moving the second pressure element from a first position to permit the passage of the liquid injection solution from the wet compartment to the dry compartment around the second pressure element. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:  
         [0018]    [0018]FIG. 1 is a cross-sectional side view of a wet/dry automatic injector assembly in accordance with the present invention;  
         [0019]    [0019]FIG. 2 is a partial cross-sectional schematic view of the wet/dry automatic injector assembly of FIG. 1; and  
         [0020]    [0020]FIG. 3 is a cross sectional side view of a wet/dry automatic injector according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    Referring now, more particularly to the figures, there is shown in FIG. 1 an automatic injector assembly  10 . The present invention is described in connection with a push button type auto injector, whereby the user removes an end cap assembly and presses a button to trigger the injection process. The present invention, however, is not limited to push button type automatic injectors; rather, it is contemplated that the present invention may be incorporated into a nose activated auto injector, as described for example in U.S. Pat. No. 5,658,259. The disclosures of which are hereby specifically incorporated herein by reference. It is also contemplated that the present invention may be adapted for use in a syringe or similar article for administering a dosage of medicament. The present invention is directed to an assembly that provides a low residual system with little dead space that may trap liquid and/or medicament.  
         [0022]    The automatic injector assembly  10  includes a generally hollow housing  110 . The housing  110  includes an injection insertion end  111  and an activation end  112 , as shown in FIG. 1. An actuator assembly  120  extends from an opening  113  in the activation end  112  of the housing  110 . The actuator assembly  120  is slidably received within the housing  110 . A removable end cap assembly  130  is releasably secured to the actuator assembly  120 . When the end cap assembly  130  is secured to the actuator assembly  120 , a side portion  131  of the end cap assembly  130  is adapted to abut the housing  110  to prevent movement of the actuator assembly  120  and unintentional injection of the medicament.  
         [0023]    The actuator assembly  120  includes a push button actuator assembly  121  having a hollow interior. The end cap assembly  130  engages the push button actuator assembly  121 . A collet  122  is located within the hollow interior of the push button actuator assembly  121 . An inner tube  123  is also located within the hollow interior of the push button actuator assembly  121 . The inner tube  123  is adapted to contact the collet  122 , as shown in FIGS. 1 and 2. An opposite end of the inner tube  123  may include an engagement rib  1231  that is adapted to be received within a complementary recess  1211  within the push button actuator assembly  121 . A drive assembly  124  is positioned within a space formed between the collet  122  and the inner tube  123 . A pin  132  extends from the end cap assembly  130  and is received within the collet  122  to prevent or block the collet  122  from collapsing prior to activation.  
         [0024]    The user removes the end cap assembly  130 . The pin  132  no longer prevents movement of the collet  122 . Upon depression of the actuator assembly  121 , the drive assembly  124  provides the necessary force when activated to operate the injector to inject the user with a necessary dosage of medicament. It is contemplated that the drive assembly  124  may be a spring assembly, a compressed gas assembly or any other suitable energy storing device. When activated, the drive assembly  124  causes the collet  122  to move such that a needle assembly  140  extends from an opening in the injection end  111  of the housing  110 . Movement of the collet  122  also causes mixing of the dry medicament with the liquid injection solution, described in greater detail below. Prior to activation, there is no pressure on the dry medicament within the dry container  160 .  
         [0025]    One end  1221  of the collet  122  extends into a wet container  150  located within the housing  110  for holding the liquid injection solution. The end  1221  of the collet  122  is adapted to contact a first plunger assembly  170  located within the wet container  150 . The first plunger assembly  170  is adapted to engage the side wall of the wet container  150  to prevent leakage of the contents (e.g. liquid injection solution) of the wet container  150  from the activation end  112  of the housing  110 . The first plunger assembly  170  is preferably formed from a material having low frictional properties such that the collet  122  and first plunger assembly  170  may easily slide within the wet container  150  when operated. Alternatively, the first plunger assembly  170  may be lubricated with silicon or other suitable non reactive lubricant. The movement of the collet  122  and the first plunger assembly  170  pressurizes the liquid located within the wet container  150 .  
         [0026]    The first plunger assembly  170  includes a central passageway  171  extending therethrough, as shown in FIG. 1. Extending through the central passageway  171  is a lance assembly  180 . The lance assembly  180  extends through the wet compartment  150  and is adapted to contact a second plunger assembly  190 , which separates the wet compartment  150  from the dry compartment  160 . The shaft  181  of the lance assembly  180  is capable of travelling within the collet  122  such that the full volume of liquid within the wet compartment  150  can be delivered to the dry compartment  160 . A suitable medicament is located within the dry container  160 . It is contemplated that the dry medicament may be in either powder or freeze-dried form. To aid in the mixture of the dry medicament with the liquid injection solution contained in the wet container  150 , it is desirable that the medicament be compressed while mixing with the liquid injection solution in the dry container  160 . The second plunger assembly  190  prevents mixing of the dry medicament and liquid injection solution prior to activation of the automatic injector assembly.  
         [0027]    The second plunger assembly  190  forms a barrier between the wet compartment  150  and the dry compartment  160 . The second plunger assembly  190  is adapted to engage the side wall of the wet container  150  to prevent passage of the contents (e.g. liquid injection solution) of the wet container  150  into the dry compartment  160  prior to activation of the automatic injection assembly. The second plunger assembly  190  is preferably formed from a material having low frictional properties such that the second plunger assembly  190  may easily slide when operated. Alternatively, the second plunger assembly  190  may be lubricated with silicon or other suitable non reactive lubricant. The movement of the second plunger assembly  190  compresses the dry medicament located within the dry container  160  and opens a fluid pathway between the wet and dry compartments  150  and  160 .  
         [0028]    During operation, the spring assembly  124  releases the collet  122 , which applies pressure on the first plunger assembly  170 . The application of pressure on the first plunger assembly  170  moves the first plunger assembly  170  in the direction of the needle assembly  140 . The first plunger assembly  170  engages the lance assembly  180  such that the fist plunger assembly  170  and the second plunger assembly  190  move together until the medicament is compressed. The first plunger assembly  170  through central passageway  171  frictionally engages the lance assembly  180 , which causes the lance assembly  180  to also move in the direction of the needle assembly  140 . The passageway  171  may engage an increased diameter section or stepped portion on the shaft  181  of the lance assembly  180 . Upon contact, the lance assembly  180  moves the second plunger assembly  190  towards the needle assembly  140 . This movement of the second plunger assembly  190  compresses the dry medicament located within the dry compartment  160  and opens a fluid passageway  200  between the wet compartment  150  and the dry compartment  160 . The first plunger assembly  170  then moves along the shaft  181  of the lance assembly  180  to pressurize and drive the liquid into the dry compartment  160 . The fluid passageway  200  may include recesses formed in the sidewall of the wet compartment  150  and the dry compartment  160 , which open upon movement of the second plunger assembly  190 . It is contemplated that the fluid passageway  200  may be formed by a reduced fit between the wet container  150  and the second plunger assembly  190 , a series of by-pass slots, a change in diameter in the compartments, ribs on the container that distort the second plunger assembly or any other assembly that is capable of permitting the flow of liquid injection solution around the second plunger assembly  190 .  
         [0029]    The movement of the collet  122  under the force of the spring assembly  124  continues to move the first plunger assembly  120  towards the needle assembly  140 . As such the liquid injection solution remains under pressure as the volume of the wet compartment  150  decreases through movement of the first plunger assembly  170 . As the first plunger assembly  170  moves along the lance assembly  180 , the frictional forces between first plunger assembly  170  and the lance assembly  180  continue to act on the lance assembly  180 , which applies pressure on the second plunger assembly  190 . With this arrangement, the dry medicament within the dry compartment  160  remains under compression. Maintaining the dry medicament under compression during to injection, accelerates the dissolution of the solid medicament into the liquid injection solution. Furthermore, this prevents the liquid injection solution entering the dry container  160  from forming channels within the dry medicament, which would impede dissolution of the medicament within the solution. As such, liquid injection solution containing less than the necessary dosage of medicament may be injected into the user.  
         [0030]    In order for the automatic injector assembly to operate effectively, the frictional forces between the second plunger assembly  190  and the side wall of the wet container  150  and the dry container  160  must be less than the frictional forces between the first plunger assembly  170  and the lance assembly  180 .  
         [0031]    The liquid injection solution mixed with the medicament may then exit the dry compartment  160  through the needle assembly  140  opposite the wet compartment  150 . A medicament support assembly  210  may be located adjacent the needle assembly  140  to prevent any undissolved medicament from entering the needle assembly  140 . The support  210  may include a filter, it may be a porous material.  
         [0032]    As discussed above, the movement of the collet  122  and drive assembly  124  causes the injection needle  141  of the needle assembly  140  to advance and protrude through the housing  110 . The injection of the medicament can be performed with a simple operation. The user simply removes the end cap assembly  130 , locates the injection end of the housing  110  adjacent the injection site and presses the push button actuator assembly  121 . This operation automatically triggers the operation of the drive assembly  124  to advance the collet  122 , which advances the first plunger assembly  170 , the lance assembly  180 , and the second plunger assembly  190  causing the liquid injection solution located within the wet compartment  150  to enter the dry compartment  160 . The dissolved medicament is then transmitted through the injection needle  141  to provide the user with the necessary dose of medicament. The automatic injector in accordance with the present invention reduces the amount of time required to administer medicament compared to other wet/dry injectors. The present invention eliminates the need for mixing by the user.  
         [0033]    It will be apparent to those skilled in the art that various modifications and variations may be made without departing from the scope of the present invention. For example, it is contemplated that a cover assembly, described for example in U.S. Pat. No. 5,295,965 (the disclosure of which is specifically incorporated herein by reference) may be secured to the injection end of the housing  110  after deployment of the medicament. Furthermore, the automatic injector may further include a nipple plunger assembly, as described for example in U.S. Pat. No. 5,465,727 (the disclosure of which is specifically incorporated herein by reference). It is also contemplated the lance assembly  180  may be connected with the second plunger assembly  190  such that the dry medicament is compressed upon movement of the lance assembly  180 . The first plunger assembly  170  may include a membrane  171  that is either applied to the plunger assembly  170  or formed as part of the plunger assembly  170 , as shown in FIG. 3. Upon application of force, the shaft  181  of the lance assembly  180  breaks through the membrane  171 . This provides an additional barrier that provides better sterility. Thus, it is intended that the present invention covers the modifications and variations of the invention, provided they come within the scope of the appended claims and their equivalents.