Dispensing device with internal drive

Claim 1

A dispensing device for delivering a beneficial agent to an environment of use, the dispensing device comprising: (a) a housing comprising a shape retaining wall that defines an internal space, which housing has at its top an opening that connects the space with the exterior of the housing, and at its bottom a retaining member that lets an external fluid enter the housing; (b) a piston in the housing that fits against the internal wall of the housing; (c) a beneficial agent compartment for storing a beneficial agent in the housing, the beneficial agent compartment defined by the space below the top opening and above the piston; and, (d) a driving compartment in the housing, the driving compartment defined by the space above the retaining member and below the piston, the driving compartment containing an osmotic device comprising: (1) a semipermeable wall that surrounds; (2) an osmotic agent compartment containing an osmotically effective solute, with; (3) a passageway through the semipermeable wall connecting the osmotic agent compartment with the exterior of the osmotic device, and wherein when in operation, beneficial agent is delivered from the dispensing device by (4) external fluid entering the dispensing device through the retaining member, and (5) being imbibed through the semipermeable wall into the osmotic agent compartment of the osmotic device to, (6) form a solution containing the osmotic solute that is pumped through the passageway from the osmotic device that, (7) fills the driving compartment, thereby (8) urging the piston forward in the dispensing device, and (9) concomitantly dispensing beneficial agent through the top opening to the environment of use.