Cartridge-holder assembly for medication dispensing unit

A cartridge assembly for a syringe-type medication dispensing unit, said assembly comprising:

• a cartridge comprising a cartridge body having first and second ends, a pierceable membrane mounted at the first end, and a piston mounted at the second end, with a volume of medication contained in the cartridge body between the membrane and the piston;
• a cartridge holder having first and second ends, said first holder end defining a central opening and means for mounting a double ended needle, said second holder end defining means for securing the holder to a medication dispensing unit and an actuating shoulder, said holder defining a central cavity shaped to receive and frictionally engage the cartridge to form an assembly which can be handled as a single, modular unit with the cartridge held securely in the holder;
• wherein the holder securing means comprises a second set of external threads;
• and
• wherein the modular unit is mounted to a syringe type medication dispensing unit having a plunger engageable with the piston, a one-way mechanism engaged with the plunger, and an actuating member for the one-way mechanism, wherein the second holder end is received within the dispensing unit, wherein the second set of external threads is engaged with the dispensing unit, and wherein the actuating shoulder is engaged with the actuating member.