A drug delivery device includes a container for storing a drug having a longitudinal axis. A plunger rod aligned with the longitudinal axis of the container has a first end and a second end, where the second end is disposed within the container. A stopper is disposed in and movable relative to the container for expelling the drug, and a drive mechanism is operatively coupled to the first end of the plunger rod. The drive mechanism is configured to deliver a drive force to move the plunger rod along the longitudinal axis and through the container. A chamber disposed between a plunger rod and the stopper is adapted to oppose the drive force of the drive mechanism.
