Dissolution rate behavior of solid cholesterol preparations in bile acid solutions

Recent work in these laboratories showed that different preparations of cholesterol monohydrate and anhydrous cholesterol had different dissolution rates under the same conditions. A method was developed by which both the thermodynamic contribution (Cs) and the interfacial kinetic contribution (P) to dissolution could be determined from experimental data. The rotating-disk dissolution method was used with the Levich theory to assess the data. Dissolution rates were determined in solutions partially saturated with cholesterol. Dynamic solubilities were determined by plotting dissolution rates (J/A) versus bulk concentration (Cb) and extrapolating to zero J/A. By using a best-fit analysis, it was possible to determine solubility as well as the interfacial transport constant independently. When this method was used to study differences in dissolution behavior of different solid preparations of cholesterol the differences could be accounted for primarily by variations in the interfacial transport constant rather than by solubility variations.