Effect of pH on the release characteristics of pentaestergum microcapsules and a study of dissolution kinetics

Rosin and rosin esters have excellent film-forming properties. Pentaerythritol-rosin ester (penta-ester gum) is found to be useful as moisture-protecting material with delayed release of drug. This communication relates the effect of pH on the release characteristics of a drug from penta-ester gum coated microcapsules. Salicylic acid granules were encapsulated using a 10 per cent solution of penta-ester gum in acetone. The microcapsules were evaluated for their drug release characteristics. Various pH media (pH 1.2, 3.0, 5.0, 7.2 and 8.0) were used. The results showed that penta-ester gum exhibits excellent resistance to higher pH levels and can be used for the sustained release of the drug. Dissolution rate constants were calculated and they agree with the assumption of Hixson and Crowell's cube-root equation.