IUD having a replenishing drug reservoir

Claim 1

An intrauterine device comprising means having a configuration exerting an anti-fertility effect when placed in the uterine cavity and drug delivery means for providing programmed delivery of drug at a rate of delivery characterized by substantially zero order time dependence for a prolonged period of at least one month, said drug delivery means comprising: a. reservoir comprising dissolved drug and undissolved replacement drug in a liquid carrier material having limited solubility for the drug and permeable to the passage of the drug, the replacement drug being present in an amount sufficient to maintain the dissolved drug in an amount substantially equal to the amount of dissolved drug originally present in the carrier material during said prolonged period; and b. a shaped wall surrounding said reservoir, said shaped wall being capable of maintaining its integrity during said prolonged period and being formed at least in part of a substantially homogeneous drug release rate controlling material permeable to the passage of the drug but having a lower permeability to the drug than the permeability thereto of the liquid carrier material; said means having a configuration exerting an antifertility effect comprising the outer configuration of said shaped wall; said shaped wall being of such size and shape to contact the sides of the uterus when said device is placed in the uterine cavity; said device when placed in the uterine cavity continuously releases drug from the reservoir at a controlled contraceptively effective rate by metered passage through the wall, the dissolved drug so released being replaced by the continuous dissolving of replacement drug in the carrier material.