Microspheres of insulin-Eudragit complex: Formulation, characterization and in vivo studies

Insulin, a hormonal drug for the management of diabetes mellitus has continued to attract attention of many researchers and pharmaceutical formulators for more than a decade. However, its low oral bioavailability due to the activities of intestinal enzymes restricts its route of administration to only the parenteral route. This study was designed to evaluate the capacity of mucoadhesive microspheres formulated with varying blends of Eudragit® RL 100 and Eudragit® RS 100 to protect insulin for oral administration. Microspheres containing varying blends of Eudragit® RL 100/RS100 loaded insulin was prepared by solvent evaporation method and were characterized in vitro and in vivo. Results showed that stable formulation with high encapsulation efficiency, positive zeta potential and high bioadhesion were obtained in all the formulations. In vitro release showed a maximum release of 9 and 87% release in pH 1.2 and 7.2, respectively. Single oral studies showed a decreased in blood glucose level comparably equal to that of subcutaneous (sc) administration. The results of this study indicate that insulin-loaded Eudragit RL100/RS100 microspheres could be a promising drug delivery system to improve oral absorption of insulin. Key words: Insulin, Eudragit®, microspheres, bioactivity, absorption.