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 automatic injection device includes a housing assembly having an interior chamber, a filter assembly, an activation assembly and a needle assembly. In accordance with the present invention, the interior chamber may include a dry compartment for storing a predetermined dry charge of dry medicament therein, and a wet compartment for storing a predetermined amount of liquid injection solution therein. The filter assembly enhances the laminar flow of fluid between the wet compartment to the dry compartment prior to the pressurization of the liquid injection solution within the wet compartment.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Serial No. 60/238,458, filed Oct. 10, 2000, and is incorporated herein in its entirety by reference 
    
    
     FIELD OF THE INVENTION 
     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 separation filter assembly that keeps the liquid material separated from the dry material until the automatic injector assembly is activated. 
     BACKGROUND OF THE INVENTION 
     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. 
     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 
     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. 
     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. 
     It is another object of the present invention to provide an automatic injector device having a separation filter assembly that separates the solid medicament from the liquid injection solution until the injector is activated. 
     It is another object of the present invention to provide an automatic injector device having a filter assembly that provides for a more laminar flow of the liquid injection solution into the dry medicament to assist in the dissolution of the dry medicament into the liquid injection solution. 
     It is another object of the present invention to provide a wet/dry automatic injector device with a solid medicament support within the device to prevent the passage of undissolved solid medicament to the needle assembly of the injector assembly thereby preventing blockage of the needle. 
     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 
     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 automatic injection device includes a housing assembly having an interior chamber, a filter assembly, an activation assembly and a needle assembly. In accordance with the present invention, the interior chamber may include a dry compartment for storing a predetermined dry charge of dry medicament therein, and a wet compartment for storing a predetermined amount of liquid injection solution therein. 
     The filter assembly is positioned between the dry compartment from the wet compartment. The filter assembly creates a laminar fluid flow of liquid injection solution as the solution passes from the wet compartment to the dry compartment. This improves dissolution of the dry medicament in the liquid injection solution. 
     The automatic injector in accordance with the present invention includes a plunger assembly positioned adjacent the filter assembly. The plunger assembly is adapted to prevent the transfer of the liquid injection solution from the wet compartment to the dry compartment prior to pressurization of the liquid injection solution within the wet compartment. In accordance with one embodiment of the present invention, the plunger assembly may include a passageway for transferring the liquid injection solution from the wet compartment to the dry compartment and a membrane assembly for preventing the transfer of the liquid injection solution from the wet compartment to the dry compartment prior to the pressurization of the liquid injection solution within the wet compartment. The membrane is designed to rupture upon pressurization of the wet compartment. In accordance with another embodiment of the present invention, the plunger assembly is adapted to moves from a first position to a second position during the pressurization of the liquid injection solution within the wet compartment. This movement opens a fluid passageway between the plunger assembly and the interior chamber to permit the passage of the liquid injection fluid from the wet compartment to the dry compartment. 
     The activation assembly pressurizes the liquid injection solution in the wet compartment, which causes the liquid injection solution in the wet compartment to be transferred to the dry compartment. The dry medicament dissolves in the liquid injection solution as the liquid injection solution passes through the dry compartment. It is contemplated that at least a portion of a plunger assembly of the activation assembly may contact the plunger assembly adjacent the filter assembly, which moves the filter and plunger assembly towards the needle assembly to force the remaining liquid injection solution and the dry medicament through the needle assembly. 
     The automatic injection device may further include a dry medicament support structure located within the interior chamber. The support structure prevents undissolved dry medicament from entering the needle assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in conjunction with the following drawing in which like reference numerals designate like elements and wherein: 
     FIG. 1 is a cross-sectional side view of a wet/dry automatic injector assembly in accordance with an embodiment of the present invention; 
     FIG. 2 is a partial cross sectional side view of a wet/dry automatic injector assembly in accordance with another embodiment of the present invention, wherein the by-pass plunger is in a closed position blocking the flow of the liquid injection solution; and 
     FIG. 3 is a partial cross sectional side view of the wet/dry automatic injector assembly of FIG. 2, wherein the by-pass plunger is in an open position permitting the flow of the liquid injection solution. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now, more particularly to the figures, there is shown in FIG. 1 an automatic injector assembly  10  in accordance with an embodiment of the present invention. 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 further contemplated that the present invention may be incorporated into a syringe assembly. 
     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 is secured to the actuator assembly  120 , a side portion  130  of the end cap assembly is adapted to abut the housing  110  to prevent movement of the actuator assembly  120  and unintentional injection of the medicament. 
     The actuator assembly  120  includes a push button actuator assembly  121  having a hollow interior. The end cap assembly 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 FIG.  1 . 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. 
     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  10  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. 
     Located within the interior of the housing  110  is a chamber  150  for housing both the liquid injection solution and the dry medicament. The liquid injection solution is located within a wet portion  151  of the chamber  150 . The dry medicament is located within a dry portion  152  of the chamber  150 . It is contemplated that the dry medicament may be in either powder or freeze-dried form. A separation filter assembly  160  separates the dry portion  152  from the wet portion  151 . The separation filter assembly  160  provides a seal to prevent seepage of the liquid injection solution into the dry portion  152  prior to activation of the injector assembly. The separation filter assembly  160  includes at least one sealing assembly  161  located around the perimeter of the filter assembly  160 . Each sealing assembly  161  engages the wall of the chamber  150 . 
     The separation filter assembly  160  may include an optional membrane assembly  162 . The membrane assembly  162  is designed to burst in response to build up of pressure within the wet portion  151  of the chamber  150  in response to movement of the collet  122 . The liquid injection solution enters an interior cavity  163  within the separation filter assembly  160  and passes through a filter  164 . The liquid injection solution then enters the dry portion  152  of the chamber  150  where it mixes with and dissolves the dry medicament. The material forming the filter  164  produces the laminar flow of the liquid injection solution. The filter  164  may include a series of channels and ribs to uniformly distribute the liquid injection solution into the dry portion  152  for mixing the dry medicament. 
     One end of the collet  122  extends into the wet portion  151  of the chamber  150  within the housing  110 . A plunger assembly  170  is secured to the end of the collet  122 , as shown in FIG.  1 . The plunger assembly  170  is adapted to engage the side wall of the wet portion  151  to prevent leakage of the contents (e.g. liquid injection solution) of the wet portion  151  from the activation end  112  of the housing  110 . The plunger assembly  170  is preferably formed from a material having low frictional properties such that the collet  122  and plunger assembly  170  may easily slide within the wet portion  151  when operated. Alternatively, the plunger assembly  170  may be lubricated with silicon or other suitable non reactive lubricant. The movement of the collet  122  and the plunger assembly  170  pressurizes the liquid injection solution located within the wet portion  151 . 
     Upon activation of the push button actuator assembly  121 , the collet  122  and plunger assembly  170  advance within the wet portion  151  of the chamber  150  toward the separation filter assembly  160 . In response to a sufficient amount of pressure within the wet portion  151 , the membrane assembly  162  ruptures and the liquid injection solution travels through the separation filter assembly  160  into the dry portion  152  to mix with the dry medicament, as described above. The mixture of the liquid injection solution and the dry medicament then exits the dry portion  152  through the injection needle  141  of the needle assembly  140 . 
     The high pressure developed within the wet portion  151  in response to movement of the collet  122  and the plunger assembly  170  forces the liquid injection solution through the separation filter assembly  160  dissolving the drug into a solution which will continue to be forced out through the needle assembly  140 . The collet  122  and plunger assembly  170  will eventually contact the separation filter assembly  160 , which causes the separation filter  160  to move in the direction of the needle assembly  140 . This action causes the remaining solution within the wet portion  151  and the dry portion  152  to be dispersed through the needle assembly  140 , which reduces the amount of residual dry medicament remaining within the chamber  150 . A filter assembly or powder support assembly  180  may be located adjacent the needle assembly  140  to prevent any undissolved medicament from entering the needle assembly  140 . 
     As discussed above, the movement of the collet  122  and drive assembly  124  causes the injection needle  141  of the injection 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, 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  causing the liquid injection solution located within the wet portion  151  to enter the dry portion  152  through the separation filter assembly  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  10  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. 
     An automatic injector assembly  20  in accordance with another embodiment of the present invention will now be described in connection with FIGS. 2 and 3. The automatic injector assembly  20  includes a by-pass plunger assembly. The injector assembly  20  has substantially the same construction as the injector assembly  10  with the exception of the provision of a by-pass plunger assembly  210  and movable filter assembly  220 . The movable filter assembly  220  includes at least one sealing assembly  221 , which engages the wall of the dry portion  152  of the chamber  150 . The by-pass plunger assembly  210  is positioned adjacent one end of the wet portion  151  of the chamber  150 . A filter assembly  220  is positioned adjacent the plunger assembly  210  in the dry portion  152  of the chamber  150 , as shown in FIG.  2 . In accordance with this embodiment of the present invention, the dry portion  152  has a larger diameter than the wet portion  151 . During operation, as the plunger  170  is moved toward the needle assembly  140 , the by-pass plunger assembly  210  is moved into the dry portion  152  of the chamber, which opens a fluid passageway  230  between the wet and dry portions of the chamber  150 , as shown in FIG.  3 . The liquid injection solution flows through the filter assembly  220 . Like the filter assembly  164 , the filter assembly  220  creates a laminar flow of the injection solution as it flows through the filter. This enhances the dissolution of the dry medicament in the liquid injection solution. 
     It is contemplated that the fluid passageway  230  may be formed by a series of by-pass slots, 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 by-pass plunger assembly  210 . 
     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). 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.