A device for delivering medicament includes a guide nut with guide ledges which cooperate with longitudinal grooves of a plunger rod for providing a rotational lock but allowing longitudinal movement of the plunger rod in relation to the guide nut that is rotationally locked to a distal housing part by engagement devices when the distal housing part and a proximal housing part are connected to each other. The device further includes a pressure release mechanism that includes slanting wedge-like surfaces arranged on the drive nut and slanting wedge-like surfaces arranged on a fixed inner annular surface of the distal housing part, which slanting wedge-like surfaces abut each other such that they move out of contact near the end of delivery of a predetermined quantity of medicament when the drive nut is rotated.
