Phenobarbitone elimination rate after oral charcoal.

Phenobarbitone elimination rate after oral charcoal Activated charcoal is used in treating poisoning by drugs to prevent their absorption. If given early and in a high dose (50 g) it will inhibit the absorption of over 90 % of most drugs.1 2A high proportion of many drugs with a long half life are excreted into the gut and reabsorbed. We report on the effect of activated charcoal, given orally in high multiple doses, on the elimination rate of three drugs with a long half life: phenobarbitone, carbamazepine, and phenylbutazone. Five healthy volunteers participated in the randomised cross-over study. After an overnight fast they swallowed the following drugs: 200 mg phenobarbitone, 400 mg carbamazepine, and 200 mg phenylbutazone. They then received either water alone or 50 g activated charcoal suspended in water either within 5 minutes or 1 hour of ingesting the drugs, or they received 50 g activated charcoal only 10 hours after the drugs, followed by and 96 hours after drug ingestion. Pheno-barbitone and phenylbutazone concentrations were estimated by gas chromatography and that of carbamazepine by spectrophotometry.2 Drug absorption was almost completely prevented by 50 g charcoal taken immediately after the drugs, whereas the effect was much weaker when 1 hour elapsed between the ingestion of the drugs and the charcoal (table).