A device is disclosed for delivering an agent to an environment of use at a substantially constant rate over time. The device comprises a wall formed of a microporous material surrounding a compartment housing the agent and a thermodynamic member. The member comprises a film formed of an expandable,...http://www.google.com.au/patents/US4235236?utm_source=gb-gplus-sharePatent US4235236 - Device for dispensing drug by combined diffusional and osmotic operations
