Selection of excipients for extended release formulations of glipizide through drug-excipient compatibility testing.

For the development of extended release formulations of glipizide, techniques of thermal and isothermal stress testing (IST) were used to assess the compatibility of glipizide with selected excipients. Initially, differential scanning calorimeter (DSC) was used to evaluate the compatibility. IR spectrum of drug-excipient mixture was also compared with that of pure drug and excipient. Compatibility of excipients defined in the prototype formula was tested using IST. Based on the DSC results alone, magnesium stearate, meglumine, TRIS buffer, and lactose, were found to exhibit interaction with glipizide. Stressed binary mixtures (stored at 50 degrees C for 3 weeks) of glipizide and meglumine showed yellow coloration indicating potential incompatibility. Based on the results of DSC, IR, and/or HPLC, excipients defined in the prototype formula were found to be compatible with glipizide. The optimized formulation developed using the compatible excipients were found to be stable after 3 months of accelerated stability studies (40 degrees C and 75% RH). Overall, compatibility of excipients with glipizide was successfully evaluated using the combination of thermal and IST methods and the formulations developed using the compatible excipients was found to be stable.