Abstract

An osmotic system for delivering a beneficial agent is disclosed. The system comprises a wall surrounding an agent compartment and an osmagent compartment separated by a film and has a passageway through the wall for delivering agent from its compartment. The wall is formed of a material permeable to the passage of an external fluid and impermeable to the passage of agent and osmagent. The film is formed of a material impermeable to the passage of agent and osmagent and movable from an original to an expanded state. The agent compartment contains an agent that is soluble in the fluid and exhibits an osmotic pressure gradient across the wall against the fluid, or the compartment contains an agent that has limited solubility in the fluid and exhibits a limited osmotic pressure gradient across the wall against fluid. The osmagent compartment contains an osmagent that exhibits an osmotic pressure gradient across the wall against the fluid. In operation, agent is delivered from the system through the passageway by fluid being imbibed through the wall into the osmagent compartment urging it to increase in volume and expand the film and correspondingly diminishing the volume of the agent compartment, whereby agent is released at a rate controlled by the permeability of the wall, the osmotic pressure gradient across the wall, and the expansion of the film over a prolonged period of time.