Accurate flow control in drug pump devices

A high-pressure drug pump device comprising:

• a drug reservoir;
• an exit member for fluidically connecting the reservoir with a drug injection site;
• a flow restrictor for restricting fluid flow through the exit member, the flow restrictor having a flow resistance factor of at least 106 μl−1;
• an electrolysis pump comprising a pump chamber in mechanical communication with the drug reservoir via an intervening displacement member, the electrolysis pump being operable to exert a pressure of at least 5 psi to drive the displacement member toward the exit member and thereby force therethrough fluid in the drug reservoir;
• and
• circuitry for operating the pump to generate a pressure of at least 5 psi, the circuitry and the flow restrictor cooperating to cause continuous fluid flow through the exit member at a constant flow rate in the range from about 400 nl/min to about 5 μl/min.