A RESERVOIR-TYPE CONTROLLED-RELEASE DEVICE USING AQUEOUS-ORGANIC PARTITIONING AND A POROUS MEMBRANE

A reservoir-type controlled release device based on aqueous-organic pa rtitioning is described. The reservoir is bounded by a microporous or porous membrane, either a hollow fiber or a flat film. The agent parti tions between phases at the aqueous-organic interface of the reservoir and the pore mouth, and then diffuses through the membrane pore into a surrounding aqueous solution. The partition coefficient significantl y influences the rate of release of the agent. The performance of the system is evaluated using model agents. Controlled release from a rese rvoir containing a pure organic liquid agent is demonstrated using tol uene. Zero-order release is achieved for benzoic acid partitioning fro m an organic reservoir into water-filled pores, and for nicotine parti tioning from an aqueous reservoir into organic-filled pores. Studies u sing benzoic acid demonstrate the effectiveness of a thin, nonporous c oating on slowing the rate of release. A fast-dissolving suspension of benzoic acid in decanol extends the duration of zero-order release. T wo agents, nicotine and caffeine, are released simultaneously and inde pendently from a divided reservoir. A simplified mathematical model is presented, and experimental results compared well with those predicte d by the model.