A controlled delivery drive mechanism includes a drive housing, a piston, and a biasing member initially retained in an energized state and is configured to bear upon an interface surface of the piston. The piston is configured to translate a plunger seal and a barrel. A tether is connected between the piston and the winch drum to restrain the free expansion of the biasing member and the free axial translation of the piston upon which the biasing member bears upon. The drive mechanism may further include a gear assembly having a motor configured to drive the gear assembly to release the tether from the winch drum. The metering of the tether by the motor controls the rate or profile of drug delivery to a user. A drug delivery pump includes such a controlled delivery drive mechanism. A control system may be utilized to control the desired drug delivery rate/profile.
