Dissolution kinetics of glibenclamide glass

This work examines the dissolution kinetics of glibenclamide crystalline state, form I, and glibenclamide glassy state, form II. This required determination of the pH-solubility profiles of the two forms, dissolution at different stirring rates, temperatures, and pHs. It was found that form II exhibited higher solubility and dissolution rate at all the studied pHs. However, a significant increase in dissolution and solubility of form II was noted at pH 6. Dissolution studies at different stirring rates confirmed that the dissolution process is diffusion controlled, zero order in nature and adheres to the Noyes and Whitney and Levich equations. Dissolution studies at different temperatures enabled calculation of the heat of dissolution, Ea, of both forms. Ea for form I and form II was found to be almost identical. Storing of form II for one week at different temperatures resulted in the partial transformation of form II to form I as indicated from dissolution studies. The extent of transformation and hence reduction in dissolution rate increased with the increase in storage temperature.