Dosage form with improved delivery capability

Claim 1

A dosage form for delivering a beneficial agent to a fluid environment of use, comprising: (a) a wall comprising in at least a part a semipermeable composition permeable to the passage of an exterior aqueous fluid and substantially impermeable to the passage of a beneficial agent, which wall surrounds and forms: (b) a compartment; (c) a first layer comprising a beneficial agent in the compartment, which layer forms in situ a dispensable aqueous formulation with fluid that enters the compartment; (d) a third layer comprising means for expanding and occupying space in the presence of fluid in the compartment; (e) a second layer interposed between the first and third layer in the compartment, said second layer a separate and distinct layer comprising a different composition than the first and third layers, which second layer comprises a non-expandable hydrophobic composition that is a means for substantially preventing the migration of the beneficial agent from the first layer comprising the dispensable aqueous formulation into the third layer; and, (f) means in the wall connecting the exterior of the dosage form with the compartment, said means for connecting the exterior of the dosage form with the interior compartment comprising a microporous member.