Imipramine Release from Ca-Alginate Gel Beads

Ca-alginate gel beads loaded with a model cationic drug imipramine were prepared, and their drug release characteristics were examiend. By soaking plain Ca-alginate gel beads in an imipramine solution, the slightly translucent beads were transformed into white beads, seemingly due to the precipitation of a drug-alginate complex. The amount of drug uptake in the beads increased linearly as the initial drug concentration increased (1-10mg/ml). However, no significant difference in uptake efficiency was observed between the beads prepared over various periods of curing time. The drug release rate from the beads was in the following order : JP XII disintegration test solution No. 1 (pH 1.2)>0.9% (w/v) NaCl≒test solution No. 2 (pH 6.8)>distilled water. The release rates were also measured in HCl solutions, NaCl solutions, and acetate buffers with varying pHs. It was suggested that imipramine ions interacting with the acidic residues of alginates were replaced by cations in the release medium and diffused out of the beads. Therefore, Ca-alginate gel could be a useful vehicle for the controlled release of water-soluble cationic drugs.