A piston rod drive system is provided comprising a main body adapted for coupling with a reservoir, a user operable activation element operatively coupled with the main body and configured to move axially and rotationally relative to the main body between a first position and a second position, and a piston rod element operatively coupled with the activation element and the main body and configured to move axially and non-rotationally relative to the main body in response to the activation element being moved between the first position and the second position.
