<p>An implantable valve accumulator pump for the delivery of medication is disclosed. The implantable pump comprises a drug reservoir maintained at constant pressure vapor. The medication metering assembly comprises a fixed volume accumulator positioned between a pair of valves. The valves alternately open and close to admit medication from the reservoir into the accumulator and to dispense a precise volume spike to an outlet catheter. In order to minimize dead volume and insure complete discharge, the accumulator employs a titanium diaphragm seated in one position by a recessed stop and in the discharge position by a spacer plate having a concentric groove pattern. The grooves are in fluid communication with the inlet and outlet. Also, a wide groove extending between inlet and outlet provides fluid communication between the grooves. The unit is externally programmed.</p>
