CHARACTERIZATION OF GLIBENCLAMIDE GLASSY STATE

Glibenclamide crystals were converted to the glassy state by cooling the melt on an ice bath. The glass state formation was confirmed by differential scanning calorimetry (DSC) measurements. Further evidence was provided by other techniques such as infrared spectroscopy (IR), X-ray powder diffraction, equilibrium solubility and dissolution studies. X-ray diffraction patterns of pulverized glassy glibenclamide stored up to 4 months at room temperature indicated no transformation to the crystalline state. The IR studies showed that the characteristic peaks of glibenclamide at 3310, 3100, 1725 and 1610 cm-1 decreased in intensity in the glassy state which was attributed to the partial transformation of the most stable keto form to the enol form during glass formation. Storing glassy glibenclamide at different temperatures resulted in a decrease in its equilibrium solubility. This decrease was attributed to the partial transformation of the glassy form to a crystalline form. The kinetics of the transformation process were pseudo first order in nature. Dissolution studies showed that glassy glibenclamide exhibits a higher dissolution rate than either crystalline glibenclamide or a commercially available product (Daonil).