Sandwiched osmotic pump tablet for controlled release of water-insoluble drug

Aim To study sandwiched osmotic pump tablet for delivering water-insoluble drug for 24 hours. Methods Sandwiched osmotic pump tablet was prepared using nifedipine as the model drug. The effects of various formulation variables and orifice size on drug release were studied. The mechanical properties of cellulose acetate membrane were also investigated. Results Polyethylene oxide of drug layer and potassium chloride of push layer showed marked positive effects on drug release. In the range of 0.50 mm to 1.40 mm, orifice size hardly affects drug release. Cellulose acetate membrane is strong enough to assure the integrity of osmotic pump tablet and could sustain an internal pressure ranging from 0.34 MPa to 2.85 MPa. Conclusion Sandwiched osmotic pump tablet can deliver water-insoluble drug constantly for 24 hours. Release media and agitation rate scarcely affect drug release. Compared with the commercialized push-pull osmotic pump tablet, sandwiched osmotic pump tablet is easy in preparation with exempting identification of drug layer before drilling.