Abstract: A surgically implantable reservoir is provided for implantation into a patient for use in an iontophoresis system for local drug delivery through a target site of internal body tissue. The reservoir comprises a housing having an inner surface defining an enclosed chamber and an inlet opening and an outlet opening for flow of fluid including the drug through the chamber. The housing is capable of interacting with a localized electric field to release the drug. A platform holding an electrode extends inwardly into the chamber from the inner surface of the housing such that the platform and an adjacent portion of the inner surface of the housing define a trough surrounding the platform. Fluid flow through the reservoir from the inlet opening to the outlet opening moves gas bubbles formed by electrolysis from the surface of the electrode and carries the bubbles through the outlet opening.