Design and Evaluation of Starch Acetate-Glipizide Microparticulate Drug Delivery Systems for Oral Controlled Release: Invitro Studies

Recently much emphasis is being laid on the development of microparticulate DDS in preference to single unit systems because of their potential benefits such as increased bioavailability, reduced risk of systemic toxicity, reduced risk of local irritation and predictable gastric emptying. The objective of the study is to prepare and evaluate starch acetate-glipizide microparticulate drug delivery systems for oral controlled release of glipizide. Spherical starch acetate- Glipizide microparticles could be prepared by the emulsification-solvent evaporation method using chloroform as solvent for starch acetate. The method is industrially feasible as it involves emulsification and removal of the solvent, which can be controlled precisely. The emulsification solvent evaporation method was reproducible with regard to size and size distribution of the microparticles. About 70-75% of microparticles in each batch were in the size range 35/50 mesh (398.5µm).Encapsulation efficiency was in the range 96.8-98.8 %. in the preparation of microparticles. Glipizide release from the starch acetate microparticles was slow and spread over longer periods of time. The drug release depended on the proportion of core:coat in the microparticles. A good linear relationship (R² = 0.874) between percent coat and release rate (ko) was observed. The relationship could be expressed by the linear equation, y = 10.5-0.167x where x is percent coat and y is release rate (ko).Glipizide release from the starch acetate microparticles was by non fickian (anomalous) diffusion. Formulation F2 prepared using a core: coat ratio of 8:2 gave slow, controlled and complete release similar to the theoretical sustained release needed for glipizide based on its pharmacokinetics. As such formulation F2 is considered as a promising microparticulate DDS for oral control release of glipizide over 12 hours for b.i.d administration.