Abstract:
Disclosed is an implant device adapted to implant medicaments into the subcutaneous portion of the patient&#39;s tissue comprising a housing having a central chamber generally in which a pusher assembly maneuvers.

Description:
This application claims the benefit of provisional application Ser. No. 60/109,684, filed Nov. 24, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an improved device for administration of pellet medicaments into the subcutaneous tissue of a mammal, and in particular to a hand-held preloaded pellet implant device capable of sequentially implanting multiple pellets into the tissue. 
     BACKGROUND OF THE INVENTION 
     Subcutaneous insertion is one method of administration of solid medicaments into a patient. The medical use of subcutaneous implants has been successfully utilized in certain treatments where it is desirable to maintain within the body a slow, constant release and absorption of a drug over an extended period of time. Delivery of hormone treatments by medical implants has proven medically successful and economically advantageous over other drug administration methods. It has been found that other forms of pharmaceutical administration such as oral and parenteral administration cause a drug to dissipate rapidly by absorption into body tissues, and thereby require a patient to undergo repeated administration. Frequent administrations of a drug treatment can be both expensive and, in the case of parenteral administrations, sometimes quite painful. On the other hand, subcutaneous drug implants, where practicable, obviate the need for frequent administrations and thus solve the problems of expense and discomfort. 
     Prior art implant delivery devices, however, have not proven successful. Several prior art devices, such as the one disclosed in U.S. Pat. No. 5,522,797, teach the use of a pellet injector gun which operates by the use of a spring or other biasing mechanism. These prior art devices are commonly used by veterinary practitioners on animals. Additionally, there are prior art devices that disclose a hand-held, manual pellet injector, but these also suffer from several major defects. For example, the devices disclosed in U.S. Pat. Nos. 3,921,632 and 4,994,028, allow the pellets to be loaded in the implanting device only after the device has been inserted into the subcutaneous tissue. The design of these prior art devices make the pellets prone to being dropped, thereby causing the medicaments to lose sterility. Further, these devices allow only one pellet to be inserted at a time and are not easily manipulable even in single pellet loading. Moreover, these implanting devices depend on gravity to keep the pellets within the implanting devices prior to actual placement within a patient. 
     The implant device of the present invention constitutes a vast improvement over the prior art devices. Use of the present implanting device obviates the need to load the pellets after the placement of the implanting device because the pellets may be pre-loaded in a plurality of laterally extending loading chambers. Also, the presence of ‘O’ rings within the loading chambers and stoppers at the top of the loading chambers prevent the pellets from falling out and thus preserve pellet sterility. Moreover, a slidably movable plunger in a disposed central hollow chamber locks after being fully retracted thereby preventing reuse and possible blood contamination. 
     It is therefore an object of the present invention to provide a pellet implanting device having a plurality of pellet loading chambers. 
     It is also an object of the present invention to provide a pellet implanting device into which a plurality of pellets may be pre-loaded prior to incising a patient. 
     It is a further object of the present invention to provide a pellet implanting device that is capable of inserting a plurality of pellets at one incision. 
     It is yet another object of the present invention to provide a disposable pellet implanting device that is adapted for a single use. 
     It is still another object of the present invention to provide a pellet implanting device wherein pellets are held securely within the loading chambers. 
     These and other objects of the present invention will become increasingly more clear upon reading the following detailed description of the preferred embodiments in conjunction with the accompanying drawings. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a device for the subcutaneous implanting of a pellet medicament into a mammal. The device includes a hollow central chamber through which a plunger assembly is slidably movable. The plunger assembly comprises a large head end in coaxial alignment with a stylet end. The stylet end of the plunger assembly is adapted to create a subcutaneous channel when inserted into and subsequently retracted from under the skin of a patient. In addition to being capable of forming a subcutaneous channel, the sides of the stylet end of the plunger are concave and slanted and therefore adapted to guide the pellets through the central chamber and into the subcutaneous channel after the stylet has been retracted into the central chamber. The interior of the central chamber further includes an automatic locking mechanism to lock the stylet end of the plunger assembly within the central chamber to prevent reuse. 
     Extending diagonally from the central chamber are a plurality of loading chambers into which medicinal pellets are pre-loaded. A finger hold is disposed proximate to a top end of the central chamber for single-handed hand use of the implant device. The interior of the loading chambers are in communication with the interior of the central chamber, but pellets are retained in the loading chambers by a plurality of ‘O’ rings disposed at the ends of the interior of the loading chambers. A manually insertable flexible prod is then utilized to push the pellets through the ‘O’ rings, then the central chamber, and then into one of the subcutaneous channels. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top perspective view of the implant device showing the stylet. 
     FIG. 2 is a cross-section view taken along line  2 — 2  in FIG.  1 . 
     FIG. 3 is a partial cross-section view of the hollow central chamber illustrating the position of the stylet when locked within the central chamber. 
     FIG. 3A is a side plan view of a flexible prod member. 
     FIG. 4 is a fragmentary side plan view of the plunger assembly. 
     FIG. 5 is a side elevation view of the implant device with a partial cross section view of the stylet partially exposed. 
     FIG. 6 is a top plan view partially in section showing the ‘O’ rings disposed within the loading chambers and an alternative finger hold at the junction where the loading chambers contact the central chamber. 
     FIG. 7 is a top plan view of the implant device illustrating stoppers on the loading chambers and stylet fully exposed. 
     FIG. 8 is a side elevation view of the implant device. 
     FIG. 9 is a detailed perspective view of the stylet end of the plunger. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, the implant device  10  includes housing  11  having a central longitudinal hollow chamber  12  formed of plastic by means of injection molding or other similarly suitable process. In the preferred embodiment, the central chamber  12  is opaque or otherwise clear to allow one to visualize the pellets in the central chamber  12 . Also in the preferred embodiment, the exterior surface of the central chamber  12  may be smooth, or alternatively, the central chamber  12  may have either a ridged or a spiraled texture. In the preferred embodiment the central chamber  12  is substantially round  31  and further includes a flat underside  30 . 
     The central chamber  12  comprises a top end  14  and a bottom end  16 . As shown in FIG. 1, integrally disposed proximate to the top end  14  of the central chamber  12  is a finger hold  18  which, in the preferred embodiment, extends from the central chamber  12  as a horizontal flat platform. The finger hold  18  assists a user of the implant device  12  in controlling the amount of force to be applied to the plunger head  24  (as described below). Referring to FIGS. 5 and 6, finger hold  18  may alternatively be a concave hourglass member  21  disposed on a plurality of loading chambers  20 , as described in greater detail below, proximate to a junction  21  where the loading chambers  20  join the central chamber  12 . In yet another embodiment, the loading chambers  20  may be angled at least 60° from the axis of the central chamber  12  to accommodate finger positioning. 
     With reference to FIGS. 3 and 4, a slidably movable plunger assembly  22 , comprising a plunger head  24  joined in coaxial alignment by a thin rod member  26  to a stylet end  28 , is substantially disposed within the hollow portion  36  of central chamber  12 . The plunger head  24  and the stylet end  28  are positioned respective to the top  14  and bottom ends  16  of the central chamber  12  wherein the plunger head  24  is disposed proximate to the exterior portion of the top end  14  of the central chamber  12 . In the preferred embodiment, the plunger head  24  is a circular platform having a circumference that is adapted for gripping by a thumb and that is greater than that of the central chamber  12 . The plunger head  24  may alternatively be comprised of any other shape suitable for gripping by a thumb. The stylet end  28  is adapted to penetrate a surface such as mammalian skin tissue. The general shape of the stylet end  28  necessarily corresponds to the shape of the hollow portion  36  of central chamber  12 . Accordingly, as seen in FIG. 9, in the preferred embodiment the shape of the stylet end  28  is substantially round with a flat underside  33 . 
     The plunger assembly  22  is longer than the length of the central chamber  12  and is slidably movable within the central chamber  12  whereby movement of the plunger assembly  22  is controlled by manual manipulation of the plunger head  24 . Referring now to FIG. 3, the diameter of the stylet end  28  at its widest point is slightly less than the diameter of the interior  36  of the central chamber  12 , which allows the plunger assembly  22  to frictionally move within the central chamber  12  when manual force is deliberately applied to the plunger head  24 . Thus, a continuous and even amount of downward pressure is applied to the plunger head  24  when the plunger head  24  is in a raised position, causes the plunger assembly  22  to steadily slide downward until the plunger head  24  abuts the top  14  of the central chamber  12 . At this point, the stylet end  28  is fully exposed from the bottom end  16  of the central chamber  12 . When the plunger head  14  is raised from the abutting position from top  14  of the central chamber  12 , the stylet end  28  is retracted within the central chamber  12 . 
     As previously stated and as illustrated in FIGS. 2 and 9, in the preferred embodiment the stylet end  28  of the plunger assembly  22  is solid and substantially conically shaped wherein a bottom surface  33  of the stylet end  28  is flat and each side  32  of the stylet end  28  is concave up to a central rib  29  (FIG.  1 ), and slanted forward to a sharp pointed end  34 . The slanting concave shape of the sides  32  of the stylet end  28  are more clearly illustrated in FIGS. 1 and 7. When the plunger head  24  is raised and the stylet end  28  is retracted from the skin of a patient, the slanting concave sides  32  of the stylet end  28  creates a distinct subcutaneous channel for pellet  42  placement, and further prevent the stylet  28  from coring skin tissue. In an alternative embodiment, the stylet end  28  may be of any known concave tip or bevel end which allows the stylet  28  to puncture skin tissue without coring any tissue or fluids. 
     Referring now to FIGS. 1,  7  and  8 , a plurality of hollow pellet loading chambers  20  extend diagonally from the central chamber  12 . The loading chambers  20  are formed of plastic by means of injection molding or other suitable process and the loading chambers  20  may be transparent to allow one to view the pellets  42  after loading. The loading chambers  20  include an inlet end  38  and an outlet end  40  (see FIG.  3 ). Pellets  42 , such as the one shown in FIG. 3, are loaded into the loading chamber  20  through the inlet end  38 , and the outlet end  40 , which is in communication with the interior  36  of the central chamber  12 , provides the egress of the pellets  42  into central chamber  12 . 
     As shown in FIGS. 3 and 6, the interior surfaces of loading chambers  20  include a plurality of deformable ‘O’ rings  44  which have a diameter substantially the same as the diameter of the pellets  42 . The ‘O’ rings  44  are disposed proximate to the inlet  38  and outlet ends  40  of the loading chambers  20  to prevent the pellets  42  from either prematurely falling into the central chamber  12 , or falling out of the loading chamber  20 , after the pellets  42  have been pre-loaded into the loading chamber  20 . After loading the desired number of pellets  42  within the loading chambers  20 , frictionally attachable stoppers  46  are fitted within each inlet end  38  of the loading chambers  20 . The stoppers  46  protect foreign contaminants from entering into the loading chambers  20  during shipment and prior to use, and prevent pellets  42  from falling out from the inlet end  38  of the loading chamber  20 . Alternatively, the stoppers  46  and the inlet end  38  of the loading chambers  20  may each be adapted for twistable attachment. 
     Referring again to FIG. 3, a locking mechanism  52  is disposed within the interior  36  of the central chamber  12  to permanently lock the plunger assembly  22  in a fully retracted position, thereby preventing the plunger assembly  22  from moving and the implant device  10  from re-use. In the preferred embodiment, the locking mechanism  52  comprises a resiliently deformable protuberance disposed on the interior  36  of the central chamber  12  proximate to the outlet ends  40  of the loading chambers  20 . The locking mechanism  52  engages a corresponding recess  50  (shown in FIG. 9) in the underside  33  of the stylet end  28 , thereby preventing the plunger assembly  22  from moving. Alternatively, a lure lock or other locking mechanism known in the art may be used in the present invention. Once locked, the plunger assembly  22  is no longer slidable and the entire implanting device  10  must be discarded. 
     When the plunger assembly  22  is engaged in the locked position, the slanting concave sides  32  of the stylet end  28  of the plunger assembly are positioned adjacent to the corresponding outlet ends  40  of the loading chambers  20 . The slanting concave sides  32  of the stylet  28  function to guide the pellets  42  from the outlet ends  40  to the bottom end  16  of central chamber  12 . 
     With reference to FIGS. 3 and 3A, a flexible prod member  54  is used to sequentially advance the pellets from the loading chambers through the ‘O’ rings  44  disposed proximate to the outlet openings  40  into the central chamber  12 . The flexible prod member  54  is molded from injected plastic or, alternatively, by another suitable means but may also be constructed from rubber or a flexible coated metal. In the preferred embodiment, the flexible prod member  54  comprises a linear, elongated member  55  having a flat end  57 . The prod member  54  is inserted in one loading chamber and then the other to advance the pellets forward and out of the chambers  20 . The flexible prod member  54  also includes a grippable loop or handle  58  disposed proximate to the center of the prod  54 . The flexible prod member  54  should be of an appropriate length whereby it may extend from the inlet end  38  of the loading chambers  20 , into the central chamber  12 , and then into the subcutaneous channels in chamber  12  formed by the stylet  28 . 
     To describe the implant procedure, the requisite number of pellets  42  are first manually loaded into the loading chambers  20  through the inlet ends  38  and past the deformable ‘O’ rings  44  disposed proximate to the inlet ends  38 . After the desired number of pellets  42  are loaded into one or both of the loading chambers  20 , the stoppers  46  are frictionally fitted onto the inlet end  38  of the loading chamber  20  to prevent contamination of the pellets  42 . Also, the plunger head  24  is initially retracted so that the stylet  28  is disposed within the central chamber  12 , however the plunger head  24  must not be fully retracted so that it does not engage the automatic locking mechanism  52 . The implant device  10  may then be positioned for insertion of the pellets  42  into a patient. 
     The bottom end  16  of the implant device  10  is positioned on the epidermal surface and an amount of downward force is applied to the plunger head  24 , thereby causing the stylet end  28  to pass through the bottom end  16  of the central chamber  12  and pierce the skin tissue and pass through to the subcutaneous layer. After reaching the desired depth, the stylet end  28  is retracted from the skin, the two concave surfaces  32  of the stylet  28  forming a subcutaenous channel in the skin of the patient. Simultaneous with the retraction of the plunger assembly  22 , the central chamber  12  is advanced through the incised skin edge to maintain the integrity of the subcutaneous channel. 
     The stylet  28  is then fully retracted to engage the automatic locking mechanism  48  and prevent reuse of the implant device  10 . Once the locking mechanism  48  is engaged, the stylet end  28  is properly positioned within chamber  36  so that the slanting concave sides  32  of the stylet  28  are adjacent to the outlet openings  40  of the loading chambers  20 . Following full retraction of the stylet  28 , the stoppers  46  covering the loading chambers  20  are removed so that the pellets  42  previously loaded in the loading chambers  20  are exposed. 
     The flexible prod  54  is used to sequentially push the pellets  42  through the deformable ‘O’ rings  44  at the outlet ends  40  of both loading chambers  20 . The pellets  42  then contact the slanting concave sides  32  of the stylet end  28  which guide the pellets toward the bottom end  16  of the central chamber  12 . The pellets  42  are then pushed through the bottom end  16  of the central chamber  12  and enter into the subcutaneous channel created by the stylet  28 . After the loaded pellets  42  are inserted into the patient, more pellets  42  may be reloaded into the loading chambers whereby the flexible prod  54  is used to push the pellets  42  into the patient. After the desired number of pellets  42  are inserted into the patient, the implant device  10  may be disposed of in an appropriate sanitary container for sharp devices. 
     The implant device  10  may be inexpensively manufactured and may be supplied as presterilized, individually packaged devices where a single implant device is discarded after a single treatment. 
     While the specific invention has been described with particular emphasis on preferred embodiments, it will be obvious to those of ordinary skill in the art that variations in the preferred embodiment of the present invention may be used and that it is intended that the invention may be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the following claims.