Abstract: A removable cartridge that is used in combination with a liquid drug infusion apparatus that comprises a housing that defines an inlet and outlet and has a recess for receiving the cartridge, a confined flow passageway extending between the inlet and outlet, and a conduit extending from the outlet to the infusion site. The removable cartridge includes: a hollow shell that fits within the recess, is adapted to contain the liquid drug, and has an outlet that is adapted to communicate with the inlet of the housing and the drug contained within the shell; pressure means within the shell that maintains a constant, positive pressure on the drug; and lock means on the shell that engages the housing to reversibly lock the cartridge within the recess.