Patent ID: 8535701

Claim:
An implantable, fluid-imbibing device for delivering an active agent to a fluid environment of use, said device comprising the following components: an impermeable reservoir comprising an interior surface; a piston that divides the reservoir into a water-swellable agent chamber and an active agent formulation chamber, wherein the water-swellable agent chamber has an open end and the active agent formulation chamber has an open end; the active agent formulation chamber comprising an active agent formulation comprising the active agent; the water-swellable agent chamber comprising a water-swellable agent; a back diffusion regulating outlet received in the open end of the active agent formulation chamber of the reservoir for delivering fluid from the active agent formulation chamber to the fluid environment, the reservoir interior surface and back diffusion regulating outlet having surfaces in a mating relationship; and a water-swellable semipermeable plug received in sealing relationship with the interior surface of the open end of the water-swellable agent chamber of the reservoir, wherein the semipermeable plug imbibes between about 0.1% and about 200% by weight of water.