A drive mechanism for utilization with a drug container in a drug pump, the drug container including a barrel and a plunger seal, comprising: a tether (525, 1525); an electrical actuator; a gear interface (101A, 1101, 1520A, 2101), rotation of the gear interface (101A, 1101, 1520A, 2101) being controlled by the electrical actuator; a gear assembly (116, 516, 1516) in rotational engagement with the gear interface (101A, 1101, 1520A, 2101), the gear assembly (116, 516, 1516) including a main gear (102, 1102) and a regulating mechanism (500, 1500), wherein the tether (525, 1525) is configured to be released from a winch assembly of the regulating mechanism (500, 1500) and the release of the tether (525, 1525) is metered by operation of the gear assembly through the regulating mechanism; a drive housing (130, 1130); a piston (110, 1110, 2110) connected to the tether (525, 1525) and configured for disposition in the barrel adjacent the plunger seal, the piston configured to translate substantially axially within the drug container; and a biasing member configured for disposition at least partially within the barrel, the biasing member being retained in an energized state between the piston and drive housing; wherein the release of the tether (525, 1525) controls the free expansion of the biasing member from its energized state and the free axial translation of the piston upon which the biasing member bears upon, and characterized in that the gear interface is configured such that a force applied to the gear interface by the gear assembly does not impact a torque causing the gear interface to rotate in that the gear interface is a rotatable shaft with one or more flanges (1101A, 2101A, 1101B, 2101B) along the length of the shaft, which one or more flanges (1101A, 2101A, 1101B, 2101B) interface with the main gear (102, 1102). a tether (525, 1525); an electrical actuator; a gear interface (101A, 1101, 1520A, 2101), rotation of the gear interface (101A, 1101, 1520A, 2101) being controlled by the electrical actuator; a gear assembly (116, 516, 1516) in rotational engagement with the gear interface (101A, 1101, 1520A, 2101), the gear assembly (116, 516, 1516) including a main gear (102, 1102) and a regulating mechanism (500, 1500), wherein the tether (525, 1525) is configured to be released from a winch assembly of the regulating mechanism (500, 1500) and the release of the tether (525, 1525) is metered by operation of the gear assembly through the regulating mechanism; a drive housing (130, 1130); a piston (110, 1110, 2110) connected to the tether (525, 1525) and configured for disposition in the barrel adjacent the plunger seal, the piston configured to translate substantially axially within the drug container; and a biasing member configured for disposition at least partially within the barrel, the biasing member being retained in an energized state between the piston and drive housing; wherein the release of the tether (525, 1525) controls the free expansion of the biasing member from its energized state and the free axial translation of the piston upon which the biasing member bears upon, and characterized in that the gear interface is configured such that a force applied to the gear interface by the gear assembly does not impact a torque causing the gear interface to rotate in that the gear interface is a rotatable shaft with one or more flanges (1101A, 2101A, 1101B, 2101B) along the length of the shaft, which one or more flanges (1101A, 2101A, 1101B, 2101B) interface with the main gear (102, 1102).