This invention relates to a method of filling a disposable drug capsule for assembly to a needleless injector, and to an article produced thereby.
Needleless injectors are used as an alternative to hypodermic syringes to inject drugs through a patient""s skin into the underlying tissues. A typical injector comprises a high pressure pump which dispenses a dose of liquid drug through a small hole with sufficient force to pierce the epidermis and diffuse into the tissues. This technique has been in use for over fifty years, and there are many patents covering various constructional details. A feature of practically all prior art injectors is that they are filled with drug by the user before injection: this has resulted in a number of inconvenient preparatory steps and the need to sterilize the drug chamber between each operation.
There has been a marked trend over the past twenty years to supply liquid drugs and other liquids for medical use pre-packedxe2x80x94for example, the familiar prefilled hypodermic syringe, or intravenous infusion bags containing a saline solution. Such presentation has several advantages: the stringent requirements for sterility are met by the manufacturer; the dosage is correct; separate vials of drug and separate syringes are not required; distribution of small quantities is facilitated; convenience and ease of use result in significant cost savings.
Needleless injectors have generally not taken advantage of these trends, and this has been a factor in the lack of widespread use of such devices. Whilst there have been attempts to use prefilled capsules, these have largely failed to address the problems and techniques associated with aseptic filling and maintaining sterility after filling. Thus, what appeared to be promising advances in the art were frustrated by the inability to aseptically fill at an economical price, and such inventions rarely progressed from laboratory prototypes.
According to the present invention there is provided a method of filling a needleless injector capsule with a drug in liquid form, and sealing the capsule after filling, the capsule defining a chamber which communicates with the exterior, prior to sealing, via an orifice in the capsule wall and an orifice in an adjacent seal held in a seal carrier, the method comprising:
(a) introducing liquid into the chamber via the seal orifice and the capsule orifice, and
(b) closing off the seal carrier to the exterior.
The invention further provides a filled and sealed drug-containing article, which comprises a needleless injector capsule defining a chamber having a drug in liquid form therein, the capsule having an orifice through a wall thereof, a seal carrier having therein a seal in which is formed an orifice communicating with the capsule orifice, and closing means for closing the seal carrier to the exterior whereby to seal off the drug in the chamber from the exterior.
A preferred embodiment comprises a hollow cylindrical capsule open at one end, and terminating in a fine hole which is the injection orifice to be placed upon the skin. A piston is slidingly and sealing located within the capsule bore adjacent to the orifice. The capsule is retained within a housing configured to connect to a needleless injector power source. Frangibly attached to the housing at the orifice end is a short tube which carries a resilient seal adapted to receive a filling needle. After filling, the filling needle is withdrawn, and a resilient plug is inserted into the short tube to form a sterile seal. During the filling process, the piston within the capsule is driven by the hydraulic pressure of the drug to some predetermined position with respect to the required fill volume. The filled capsule is then attached to the injector energy source. Before use, the frangibly connected tube is snapped off complete with the resilient seals, thus exposing the capsule orifice. The injector is then operated according to the required methodology.