Effect of cholestyramine on the gastrointestinal absorption of phenprocoumon and acetylosalicylic acid in man

Summary The effect of cholestyramine on the absorption of phenprocoumon and acetylosalicylic acid has been studied in volunteers by comparing their serum concentrations after a single oral dose either of the drug alone or simultaneously with the resin in a crossover repetition arrangement. In four volunteers cholestyramine 8 g significantly reduced the absorption of a simultaneous 15 mg dose of phenprocoumon. The effect of the latter on coagulation, as measured by the thrombotest method was also diminished. The absorption of acetylosalicylic acid 500 mg was delayed by cholestyramine but there was no appreciable effect on the total amount absorbed. These results are in accordance with the stronger binding of phenprocoumon to cholestyramine inin vitro experiments.