A drive mechanism 2100, 3100 includes a housing 2130, a piston 2110 adapted to impart movement to a plunger seal 2060 within a drug container 2050, a plurality of biasing members 2106, 2122 disposed in parallel, and a retainer 2115. The biasing members 2106, 2122 are disposed to release energy to cause movement of the piston 2110 from a retracted first position to the extended second position, the piston 2110 bearing against the plunger seal 2060 to dispense medicine. The retainer 2115 is disposed to maintain the biasing members 2106, 2122 in the energized position and to release the biasing members 2106, 2122 to permit the piston 2110 to dispense the medicine. The drive mechanism 2100, 3100 may also include an end-of-dose indicator 2133, 3133 to identify at least one of when the sleeve assembly 2120, 3120 is disposed subjacent a window 2131, 3131 in the housing 2130, 3130 the relative motion of the sleeve assembly 2120, 3120 with reference to the window 2131, 3131 or another reference component, the stoppage of such motion, and the rated or change of rate of motion.
