Abstract: The subject patient controlled analgesia (PCA) apparatus is mechanical/hydraulic and comprises a reservoir and a pump operable by the patient for dispensing medicine from the reservoir unto the patient's IV system in incremental doses. The pump capacity per stroke may be adjustable, thereby adjusting the size of each dose dispensed. Timing apparatus assures that a specific interval of time (the lockout interval) must pass between sequential dosage dispensations. Check valves in the passages for pumping the medicine and filling the apparatus are double in series to reduce chances of malfunction or misuse due to valve failure. The quantity of medicine in the reservoir is indicated.