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 dry compartment located within a housing for storing a predetermined dry charge of the medicament therein, a wet compartment within the housing for storing a predetermined amount of liquid injection solution therein, an activation assembly for causing the liquid injection solution in the wet compartment to be transferred to the dry wet compartment, and at least one compression assembly for maintaining the medicament located in the dry compartment under a continuous compressive state as the liquid injection solution passes through the dry compartment.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims priority from U.S. Provisional Serial No. 60/209,974, filed Jun. 8, 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.  
         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 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 stores the solid medicament under pressure to enhance dissolution in the liquid injection solution.  
           [0008]    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  
         [0009]    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 may include a housing assembly, a dry compartment located within the housing for storing a predetermined dry charge of the medicament therein, a wet compartment within the housing for storing a predetermined amount of liquid injection solution therein, and an activation assembly for causing the liquid injection solution in the wet compartment to be transferred to the dry compartment. In accordance with the present invention, the medicament located within the dry compartment dissolves in the liquid injection solution as the liquid injection solution passes through the dry compartment to the needle.  
           [0010]    The automatic injector in accordance with the present invention further includes at least one compression assembly for maintaining the medicament located in the dry compartment under a continuous compressive state as the liquid injection solution passes through the dry compartment. As such the undissolved medicament is maintained in a compressive state. In accordance with the present invention, the at least one compression assembly is located within the dry compartment. Each compression assembly may include an expandable assembly. The expandable assembly expands as the medicament located within the dry compartment dissolves within the liquid injection solution. The expandable assembly may include a spring assembly and at least one plate to apply pressure on the medicament within the dry compartment. The at least one plate permits the passage of the liquid injection solution therethrough.  
           [0011]    The automatic injector in accordance with the present invention further includes a needle assembly for dispensing the liquid injection solution containing the medicament dissolved therein.  
           [0012]    The automatic injector in accordance with the present invention may further include a releasable liquid barrier assembly located between the wet compartment and the dry compartment for selectively preventing passage of the liquid injection solution from the wet compartment to the dry compartment at predetermined conditions. It is contemplated that the releasable liquid barrier assembly permits the passage of the liquid injection solution to the dry compartment in response to a predetermined liquid pressure build up within the wet compartment.  
           [0013]    In another aspect of the invention, a method for administering an injection of medicament injection solution to a patient using an automatic injection device is provided. Generally, the method comprising locating an injection end of the automatic injection device adjacent a desired injection site on the patient; and activating a drive to advance a collet into a wet compartment of the automatic injection device to pressurize the liquid injection solution in the liquid compartment and to cause an injection needle of the automatic injection device to advance and protrude through the injection end of the automatic injection device. The pressurization of the liquid injection solution causes the liquid injection solution to pass into a dry compartment adjacent the wet compartment where the liquid injection solution mixes with a compressed dry medicament to form a medicament injection solution which is then transmitted through the injection needle to the injection site where it is administered to the patient. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:  
         [0015]    [0015]FIG. 1 is a cross-sectional side view of a wet/dry automatic injector assembly in accordance with the present invention;  
         [0016]    [0016]FIG. 2 is a partial cross-sectional schematic view of the wet/dry automatic injector assembly of FIG. 1;  
         [0017]    [0017]FIG. 3 is a partial cut-away view of the injection end of the wet/dry automatic injector assembly of FIG. 1; and  
         [0018]    [0018]FIG. 4 is a partial schematic view of a barrier layer assembly of the wet/dry automatic injector assembly according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    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.  
         [0020]    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.  
         [0021]    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 .  
         [0022]    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.  
         [0023]    One end of the collet  122  extends into a wet container  150  located within the housing  110 . A sealing assembly  1221  is secured to the end of the collet  122 , as shown in FIGS. 1 and 2. The sealing assembly  1221  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 sealing assembly  1221  is preferably formed from a material having low frictional properties such that the collet  122  and sealing assembly  1221  may easily slide within the wet container  150  when operated. Alternatively, the sealing assembly  1221  may be lubricated with silicon or other suitable non reactive lubricant. The movement of the collet  122  and the sealing assembly  1221  pressurizes the liquid located within the wet container  150 . One end of the wet container  150  opposite the sealing assembly  1221  includes an aperture  151  therein. When pressurized by movement of the collet  122 , the liquid exits the wet container  150  through the opening  151  to the dry container  160 , which contains the dry medicament in solid form.  
         [0024]    A liquid barrier assembly  170  is located adjacent the opening  151  to prevent the inadvertent passage of liquid from the wet container  150  to the dry container  160 . As shown, the liquid barrier assembly  170  includes a movable plunger assembly slidably received within the dry container  160 . The plunger assembly engages the side wall of the dry container  160  such that liquid does not pass to the dry medicament contained within the dry container  160 . As pressure within the wet container  150  increases, the plunger assembly  170  moves away from the opening  151 . The dry container  160  includes a recess  161  in a side wall. Liquid may pass from the wet container  150  to the dry container  160  when the plunger assembly  170  is received within the recess  161 . The recess  161  allows liquid to flow around the plunger assembly  170  to the dry medicament located within the dry container  160 .  
         [0025]    The present invention is not limited to the above-described arrangement of the dry container  160  and the wet container  150 ; rather, other variations are considered to be well within the scope of the present invention. For example, the each of the containers  150  and  160  may the same diameter. Furthermore, a single compartment having a divider assembly may be provided to separate the liquid injector solution from the dry medicament.  
         [0026]    The present invention is not limited to the above-described plunger assembly  170 ; rather, it is contemplated that other liquid barrier assemblies may be employed. The liquid barrier assembly must also prevent vapor transmission between the wet container  150  and the dry container  160 . For example, the plunger assembly may be replaced with a barrier layer. The barrier layer would distort and subsequently rupture upon a sufficient build up of pressure within the wet container  150 . The barrier layer may be formed from any suitable non reactive impermeable material that could rupture at a predetermined pressure.  
         [0027]    It is also contemplated that the barrier layer may be pierced by a piercing element located within the housing  110 . For example, a piercing element may extend from the sealing assembly  1221  such that upon a predetermined movement of the collet  122 , the piercing element pierces the barrier layer to permit the liquid to flow from the wet container  150  to the dry container  160 . Alternatively, the liquid barrier assembly may include a piercing element  270  extending from a compression element  180 , as shown in FIG. 4. As pressure within the wet container  150  increases the barrier layer  271  distorts. A puncture within the barrier layer  271  is created when the layer  271  contacts the piercing element  270 . A retainer assembly  272  may be located between the barrier layer  271  and the compression element  180  such that a sufficient distance exists between the barrier layer  271  and the piercing element  270  to allow for a sufficient build up in pressure.  
         [0028]    The dry container  160  will now be described in greater detail. 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 maintained in a compressed state while in the dry container  160 . 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. The compression element  180  prevents this phenomenon.  
         [0029]    The compression element  180 , illustrated in FIG. 1, includes at least one assembly having the ability to expand to compensate for the dissolution of the medicament within dry compartment  160 . The compression element  180  may include a spring assembly  181  sandwiched between a pair of liquid permeable plates  182  and  183 . It is contemplated that any suitable spring assembly may be employed provided that the expansion of the spring assembly is capable of compensating for the dissolution of the medicament within the dry compartment  160  such that undissolved dry medicament is maintained in a compressed state. The spring assembly may be formed from a non-reactive stainless steel material. Other materials having similar non-reactive properties are considered to be well within the scope of the present invention. Furthermore, it is contemplated that the spring assembly may be coated with a suitable non-reactive material including, but not limited to Teflon®.  
         [0030]    The embodiment of the present invention illustrated in FIGS. 1 and 2 illustrates a single compression element  180  located within the dry compartment  160 . It, however, is contemplated that additional compression elements may be employed. For example, the medicament located within the dry compartment  160  may be sandwiched between a pair of compression elements. Each compression element may include the above described spring assembly and liquid permeable plates. An example of this arrangement is illustrated in FIGS. 14 and 15 of U.S. Pat. No. 5,725,777 to Taylor, entitled “Reagent/Drug Cartridge,” the disclosure of which is incorporated herein specifically by reference.  
         [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 . In the event that two compression elements are utilized, the liquid injection solution mixed with the medicament will pass through one of the compression elements to the needle assembly  140  prior to exiting through the opening. A filter assembly, not shown, may be located adjacent the needle assembly  140  to prevent any undissolved medicament from entering the needle assembly  140 . Additionally, a liquid impermeable membrane, not shown, may be provided to prevent the undesired passage of liquid in the event the liquid inadvertently enters the dry compartment  160 . The membrane may be either be punctured by the injection assembly  140  or rupture upon the build up of a sufficient amount of pressure.  
         [0032]    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  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  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. 5,295,965 (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.