Novel drug delivery device

Claim 1

A delivery device for the controlled and continuous administration of drug to a body site over a prolonged period of time, said device comprising: a. a means for containing and releasing the drug at a controlled rate comprising a reservoir containing a dissolved drug portion and an undissolved replacement drug portion in a liquid carrier material permeable to the passage of the drug therethrough, said drug having limited solubility in said liquid carrier material; the replacement drug portion being present in an amount in excess of its solubility in the carrier material and in an amount sufficient to maintain the amount of the dissolved drug portion substantially constant during said prolonged period of time, said means further comprising: b. a shaped wall that surrounds the reservoir and is characterized by being insoluble in body fluid, maintaining its integrity during said prolonged period of time, and by being formed at least in part of a microporous polymer housing in its micropores a drug release rate controlling medium permeable to the passage of the drug but having a lower permeability to the drug than the permeability of the liquid carrier material to the drug; so that the device when placed at the body site, continuously releases drug from the reservoir of the body site at a physiologically or pharmacologically effective controlled rate by metered passage through the medium, the dissolved drug so released being replaced by the continuous dissolving of replacement drug in the carrier material so as to substantially maintain the amount of dissolved drug in the reservoir substantially constant during said prolonged time period.