1. Preparation and evaluation for controlled release of olibanum resin coated microcapsules of carbamazepine

The objective of the study is to evaluate olibanum resin, a natural lipophilic polymer for its application as microencapsulating agent and to prepare and evaluate olibanum resin-coated microcapsules of carbamazepine for controlled release. Controlled release formulations are needed for carbamazepine to avoid erratic absorption, fluctuating plasma concentrations and associated toxicity and patient compliance. Olibanum resin coated microcapsules of carbamazepine were prepared by emulsification-solvent evaporation method and the microcapsules were evaluated for controlled release. The resin coated microcapsules prepared are spherical, discrete, free flowing and were of multinucleate and monolithic type. Microencapsulation efficiency was in the range 99.0-100.7%. Carbamazepine release from the microcapsules was slow over 24h and depended on core:coat ratio, wall thickness and size of the microcapsules. Drug release was by Fickian diffusion when the drug release was relatively rapid as in the case of microcapsules of smaller size, OMC1, OMC2 and OMC3 of size 35/50. The release was by non-Fickian diffusion when the drug release was more slow as in the case of all microcapsules of size 20/35 and microcapsules, OMC4 of size 35/50. Good linear relationship was observed between wall thickness of the microcapsules and release rate. Olibanum resin was found suitable as a new microencapsulating agent and the resin coated microcapsules exhibited good controlled release characteristics. Carbamazepine release from the olibanum resin coated microcapsules, OMC3 (size 20/35) was similar to that from Trigretal CR tablets, a commercial controlled release formulation of carbamazepine.