A drive mechanism including a housing, a piston adapted to impart movement to a plunger seal within a drug container, a plurality of biasing members disposed in parallel, and a retainer. The biasing members are disposed to release energy to cause movement of the piston from a retracted first position to the extended second position, the piston bearing against the plunger seal to dispense medicine. The retainer is disposed to maintain the biasing members in the energized position and to release the biasing members to permit the piston to dispense the medicine. The drive mechanism may also include an end-of-dose indicator to identify at least one of when the sleeve assembly is disposed subjacent a window in the housing, the relative motion of the sleeve assembly with reference to the window or another reference component, the stoppage of such motion, and the rated or change of rate of motion.
