A patient controlled liquid drug administration device comprises a reciprocating pump having an inlet connectable to a source of a pressurized liquid drug and an outlet connectable to the patient. A clamp rotates between closed and open positions respectively blocking and enabling pump outflow. A plunger above the pump has an end contacting a movable wall of the pump and is movable between raised and lowered positions. A button above the plunger moves between extended and depressed positions and has a ledge that engages the clamp when the button is moved to the depressed position and moves the clamp to its open position. A compression spring is disposed between the plunger and the button. A spring catch engages a detent in the button when the button is moved to its depressed position and holds the button there until released by a catch release ON the plunger that disengages the spring catch from the detent in the button when the plunger is moved to its lowered position. A removable tab permits easy, rapid priming of the pump by holding the clamp in its open position regardless of the position of the button and by holding the button in its depressed position regardless of the position of the plunger.
