Patent ID: 7201746

Claim:
An implantable therapeutic substance delivery device comprising: a housing; a therapeutic substance reservoir carried in the housing, the therapeutic substance reservoir having a reservoir outlet; a power source carried in the housing; electronics coupled to the power source; and, a piston pump coupled to the electronics and coupled to the reservoir outlet, the piston pump comprising a pump cylinder in which a pump piston moves and an inlet chamber in fluid communication with a pumping chamber through a fluid path in the pump cylinder, wherein the piston pump is configured for pumping therapeutic substance from the therapeutic substance reservoir through an infusion port at a programmed rate; an inlet valve in fluid communication with the reservoir, the inlet valve configured for controlling therapeutic substance flow from the inlet chamber into the pumping chamber; and an anti-cavitation valve in fluid communication with the reservoir outlet and the inlet chamber, the anti-cavitation substantially preventing retrograde flow of therapeutic substance from the inlet chamber back toward the reservoir outlet.