Adsorption of sulfonylureas onto activated charcoal in vitro

Adsorption of carbutamide, chlorpropamide, tolazamide, tolbutamide, glibenclamide (glyburide), and glipizide onto activated charcoal was compared in vitro using different charcoal-to-drug ratios. Maximal binding capacities of different sulfonylureas were 0.45-0.52 g/g of charcoal at pH 7.5. The affinity of the second generation derivatives, glibenclamide and glipizide, was considerably higher than that of the first generation derivatives. The affinity of sulfonylureas to charcoal was higher at pH 4.9 than at pH 7.5. Poor water solubility of sulfonylureas at pH 1 prevents the adequate testing in these conditions. Contrary to what has appeared previously, activated charcoal effectively adsorbs different sulfonylureas and can be used to possibly prevent their gastrointestinal absorption.