CALORIMETRIC EVALUATION OF HYDRATION OF CHOLESTYRAMINE

We have investigated the mechanism of hydration of cholestyramine, a w ater-insoluble resin used pharmaceutically. Two types of water of hydr ation (freezing and non-freezing) and the amounts of heat evolved or a bsorbed during the hydration of cholestyramine were determined. From d ifferential scanning calorimetry, 0.57 g water was observed to be tigh tly bound per gram of resin (non-freezing water). The hydration of dry cholestyramine was found to be exothermic. The heats of hydration of cholestyramine with chloride or nitrate counter-anions were found to b e -6.05 and -3.46 cal g(-1), respectively. Some of the partially hydra ted cholestyramine samples showed absorption of heat during hydration. The data generated in the study were utilized to better understand th e mechanism of hydration and swelling of cholestyramine.