IMIPRAMINE RELEASE FROM CA-ALGINATE GEL BEADS

Ca-alginate gel beads loaded with a model cationic drug imipramine wer e prepared, and their drug release characteristics were examined. By s oaking plain Ca-alginate gel beads in an imipramine solution, the slig htly translucent beads were transformed into white beads, seemingly du e to the precipitation of a drug-alginate complex. The amount of drug uptake in the beads increased linearly as the initial drug concentrati on increased (1-10 mg/ml). However, no significant difference in uptak e efficiency was observed between the beads prepared over various peri ods of curing time. The drug release rate from the beads was in the fo llowing order: JP XII disintegration test solution No. 1 (pH 1.2) > 0. 9% (w/v) NaCl is-approximately-equal-to test solution No. 2 (pH 6.8) > distilled water. The release rates were also measured in HCl solution s, NaCl solutions, and acetate buffers with varying pHs. It was sugges ted that imipramine ions interacting with the acidic residues of algin ates were replaced by cations in the release medium and diffused out o f the beads. Therefore, Ca-alginate gel could be a useful vehicle for the controlled release of water-soluble cationic drugs.