| abstract |
An osmotic device that, following the imbibition water vapor, provides for the controlled release of a beneficial agent to a non-aqueous environment. The device comprises a hydrophilic formulation and a beneficial agent, surrounded by a wall. The wall is formed at least in part of a semipermeable hydrophobic microporous membrane having an average pores size between about 0.1 mu m and 30 mu m. The pores are substantially filled with a gas phase. The hydrophobic membrane is permeable to water in the vapor phase and the hydrophobic membrane is impermeable to an aqueous medium at a pressure less than about 100 Pa. The beneficial agent is released, for example, by osmotic pumping or osmotic bursting upon imbibition of sufficient water vapor into the hydrophilic formulation. The high water fluxes attendant with these vapor-permeable hydrophobic membranes facilitate the delivery of large quantities of beneficial agents without requiring large surface areas (quantities) of hydrophobic microporous membrane. In addition, use of vapor-permeable hydrophobic microporous membranes allow osmotic devices to be used in environments having limited water availability, such as air or soil. |