Patent ID: 8679095

Claim:
A drug delivery system for implantation in a body for delivery of a liquid drug, the system comprising: a) a housing having a chamber; b) a diaphragm dividing the chamber into a first subchamber in a first flow path and a second subchamber in a second flow path; c) the diaphragm moveable in response to difference in pressure between the first subchamber and the second subchamber to regulate pressure difference between the first flow path and the second flow path; d) a valve operatively linked with the diaphragm to open the first flow path when pressure in the second flow path exceeds pressure in the first flow path by a predetermined amount; e) a pump having an inlet in fluid communication with the first flow path and an outlet in fluid communication with the second flow path; f) an infusion pump housing defining a drug reservoir; g) a propellant chamber within the pump housing and proximate the drug reservoir, wherein pressure is exerted on the drug reservoir; and h) the drug reservoir having a reservoir inlet for receiving the liquid drug and a reservoir outlet, the outlet in fluid communication with the first flow path, whereby the liquid drug is delivered independent of changes in reservoir pressure and ambient pressure.