Abstract: A device for the continuous administration of a diffusible agent having a relatively rapid rate of diffusion and a diffusible agent having a relatively show rate of diffusion comprises:a wall, formed at least in part by a porous membrane, which surrounds and defines a reservoir, the reservoir comprising:(a) a compartment which comprises the agent having the relatively slow rate of diffusion, wherein said compartment is in direct contact with the porous membrane part of the wall and(b) at least one compartment which comprises the agent having the relatively rapid rate of diffusion, wherein said compartment is not in direct contact with the porous membrane part of the wall and is separated from the compartment comprising the agent having the relatively slow rate of diffusion by a porous partition, such that when said device is exposed to said fluid medium, said agents will diffuse through the porous membrane part of said wall at a substantially steady rate for a prolonged period of time.