A multi-stage drug delivery system having a cartridge and multiple plungers positioned in the cartridge and spaced apart from one another is provided. A first plunger, a second plunger, and the cartridge form a first chamber storing a first drug. The second plunger and the cartridge form a second chamber storing a second drug. A cannula pierces the first plunger to access the first drug. As the first plunger is driven toward the second plunger, the first drug is expelled from the first chamber for delivery to a patient through the cannula. After expelling the first liquid drug, the cannula can pierce the second plunger to access the second drug. As the first and second plungers are together driven toward a closed end of the cartridge, the second liquid drug is expelled from the second chamber for delivery to the patient through the cannula.