Effect of ethanol and pH on the adsorption of drugs to activated charcoal: studies in vitro and in man.

The effect of ethanol on the adsorption of aspirin, quinidine and amitriptyline to activated charcoal was studied in vitro at pH 1.2 and 7.0. The adsorption of these drugs was greatly dependent on the charcoal-drug ratio and on the pH. Ethanol (10%) significantly (P less than 0.001) increased the percentage of their unadsorbed fraction at both pHs in vitro. In six healthy volunteers activated charcoal (50 g), ingested 5 min. after aspirin (1000 mg) and quinidine sulfate (200 mg), reduced their bioavailability by about 70% (aspirin) and 99% (quinidine). A significant desorption of aspirin but not that of quinidine from charcoal was obvious on the second and third days and seemed to be related to the effect of pH. The absorption of ethanol was not significantly prevented by charcoal. The concomitant ingestion of alcohol (50 g) with drugs antagonized only slightly the ability of charcoal to reduce the absorption of aspirin and quinidine.