Cartridge injector for pellet medicaments

An improved device for subcutaneous implantation of single and plural elongated medicament pellets comprising a single dosage where magazine feeding is not applicable because considerations of sterility and cross-contamination require a fresh needle and obturator for each patient. The device includes a cannula supported at a proximal end thereof by a hub which slides within a tubular barrel, the barrel supporting an obturator which selectively penetrates the cannula to maintain an implanted pellet in position as the cannula is withdrawn. For single pellet dosages, the pellet is carried in the fore part of the cannula, while in the case of multiple pellet dosages, the additional pellets, prior to loading, are carried in open-ended cylindrical tubes engageable with a proximal end of the hub whereby the obturator may be employed to transfer the pellet to the cannula from the sleeve which is discarded. Repositioning of the hub within the sleeve is then accomplished without disengagement of the distal end of the cannula from the tissues of the patient and additional implantations may then be performed.

BACKGROUND OF THE INVENTION 
This invention relates generally to the field of devices for the 
subcutaneous implantation of pellet medicaments of the type described in 
my prior U.S. Pat. No. 4,451,253 granted Apr. 29, 1984. More particularly, 
it relates to an improved form thereof particularly suited for the 
implanting of a plurality of pellets comprising a single dosage into human 
beings, as contrasted with mechanical type devices used widely in the 
field of veterinary medicine for administering single dosages serially to 
plural animals, where problems of sterility are of lesser moment. 
One recently developed system of human contraception requires the 
implantation of a pair of medicament pellets in generally juxtaposed 
subcutaneous relation. The pellets are of high sectional density, i.e. 
quite elongated in relation to cross-sectional diameter and may be 
relatively fragile. For this reason, it is desirable to implant the 
pellets in a manner in which the implanting needle is withdrawn as the 
pellet is maintained in position by a relatively non-moving obturator in 
the manner described in my above-mentioned prior patent. Further, the 
sterility of both pellets and of the cannula and obturator must be 
maintained on a continuous basis. 
SUMMARY OF THE INVENTION 
Briefly stated, the invention contemplates the provision of an improved 
implanting device of the type described in which the above-mentioned 
desirata are obtained in which the device may be of disposable single use 
type thereby eliminating the necessity of sterilization in the field, or 
in the alternative, where desired, the device may be resterilized between 
applications and reused. To provide for multiple pellet dosage, the 
pellets are enclosed and sterilized in open-ended sleeves which are 
capable of being used as chargers to position additional pellets in the 
barrel of the device without the necessity of removing the cannula from 
engagement with the patient. The sleeves allow loading of one or more 
additional pellets without direct contact between the hand of the operator 
and the surface of the pellets, thus maintaining the sterility of the 
pellets. 
The device comprises a hub having finger-engaging means whereby it is 
slidably related to a slotted barrel, one end of which mounts a proximal 
end of an obturator. The distal end of the obturator penetrates a cannula, 
the proximal end of which is secured to the hub. Movement of the 
finger-engaging means relative to the barrel results in the obturator 
moving through the cannula to maintain an implanted pellet in position as 
the cannula is withdrawn. The hub is provided with an arcuate recess in a 
proximal end surface thereof which accommodates an open end of a sleeve 
carrying a second pellet, so that with the disengagement of the barrel 
from the hub, the sleeve may be engaged at one end thereof, wherein the 
distal end of the obturator may be used to move a second pellet into the 
cannula for subsequent implantation. The barrel is then reengaged with the 
hub for the implantation of the second pellet after slightly altering the 
angle of the cannula relative to the site of the implantation. The 
proximal end of the barrel is of sufficient length that it can accommodate 
a sleeve engaged in the hub when the hub is fully withdrawn. The sleeve is 
discarded with the next disengagement of the hub from the barrel.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT 
In accordance with the invention, the device, generally indicated by 
reference character 10, comprises a barrel element 11 (FIG. 2.) which 
serves as a manually engageable handle, and may be formed of either 
metallic or synthetic resinous materials. It is bounded by an outer 
surface 12, an inner surface 13, a proximal end 14 and a distal end 15. 
Extending from the distal end 15 is an elongated slot 16 extending between 
an open end 17 and a closed end 18. The slot includes a distal lock notch 
and a proximal lock notch, the purpose of which will become more clearly 
apparent at a later point in this disclosure. 
Referring to FIG. 1 in the drawing, a cannula element 21 includes a hollow 
cannula or needle 22 of inner diameter corresponding to a medicament 
pellet. It includes a sharpened distal end 23 and a proximal end 24 bonded 
to a molded hub member 25. The hub member 25 includes a hollow cylindrical 
body 26 which surrounds the proximal end of the cannula and a laterally 
extending flange 27 which is conveniently manually engaged by the thumb of 
the user. A finger-engaging surface 28 thereof may contain suitable 
grooving for this purpose. 
Referring to FIG. 4, although not essential, the cannula element is 
preferably protected prior to use by a cover member 30, a closed distal 
end 31 of which may be provided with a peg 30A which enters the distal end 
of the cannula to maintain a pellet in position during shipping, etc. The 
open proximal end 32 is preferably frictionally retained upon the hub 
member 25 until the device is used. 
Referring to FIG. 3, a cylindrical obturator 33 is engaged at the proximal 
end 34 thereof in a retaining well 35 in the barrelelement 11. The distal 
end 36 is thereby positioned to penetrate the cannula in sliding relation. 
Referring to FIG. 5., there is illustrated a medicament pellet element in 
the form of a cartridge which comprises an elongated medicament pellet 39 
and a surrounding polyethylene sleeve 40 having first and second open ends 
41 and 42, respectively. Preferably, the sleeve 40 is slightly longer than 
the pellet 39. 
As best seen in FIG. 6., reference character 43 designates a 
cylindrically-shaped recess in the proximal end 44 of the hub member 25 of 
diamter corresponding to that of at least one of the open ends 41 and 42. 
Where the device is used for implanted multiple elongated pellets as part 
of a single dosage, the device may be sterilly packed with the first 
pellet already loaded within the cannula, and the additional required 
pellets may be packed with surrounding sleeves 40. After removing the 
cover member 37, the cannula is inserted subcutaneously to a depth 
sufficient to allow the pellet to be completely implanted (the outer 
surface of the cannula may be suitably marked for this purpose), following 
which the flange 27 is moved from the distal lock notch 19 into alignment 
with the slot 16, and thence to the rear of the proximal lock notch 20. 
This will result in withdrawal of the cannula while the obturator, 
entering the cannula maintains the pellet in implanted condition. 
While maintaining the distal end of the cannula in engagement with the 
patient, a reverse motion of the flange permits the barrel element to the 
disconnected from the hub, and a pellet cartridge element 38 may then be 
engaged within the recess 43 for reloading. The hub is then reengaged with 
the barrel element, and after slightly altering the angle of engagement of 
the cannula with the patient, the implanting action is repeated. The 
reengagement of the barrel element with the hub will result in engagement 
by the distal end of the obturator with the free end of the sleeve 40, and 
the transfer of the pellet 39 to the cannula. Further movement of the hub 
member 25 within the slot 16 will result in the implantation of the second 
pellet. 
Where the device is used for a single implantation, upon the completion 
thereof, the hub flange may be engaged with the proximal lock notch to 
maintain the cannula within the barrel, so that it may be conveniently 
discarded without danger of injury to personnel. 
Turning to the modified form of the invention shown in FIG. 7, parts 
corresponding to those of the principal form have been designated with a 
similar reference characters, with the additional prefix "1". 
This modification differs from the principal form in the elongation of the 
barrel 112 and obturator 133 so as to provide additional room for the 
storing of empty sleeves 40 where the device is used for implanting a 
plurality of cartridges comprising a pellet and sleeve (FIG. 5). With the 
additional length, the sleeves 40 may be collapsed and stored in the area 
indicated by reference character 113, and may be removed, if the device is 
to be used, by merely disengaging the obturator 133 therefrom. 
I wish it to be understood that I do not consider the invention to be 
limited to the precise details of structure shown and set forth in the 
proceding specification, for obvious modifications will occur to those 
skilled in the art to which the invention pertains.