ACCELERATION OF THE BODY CLEARANCE OF PHENOBARBITAL BY ORAL ACTIVATED-CHARCOAL

The effect of multiple oral doses of activated charcoal on the pharmacokientics of i.v. phenobarbital was studied in a randomized crossover trial. Six healthy men volunteered to take 200 mg phenobarbital sodium/70 kg body wt i.v. on 2 separate occasions. Each subject received oral activated charcoal (180 g) in divided doses over 3 days after the infusion of phenobarbital. Serum levels of phenobarbital were measured in all subjects up to 90 h after the infusion, and urinary excretion of phenobarbital was measured in 2 subjects 24-96 h after the infusion. A pharmacokinetic analysis showed that the charcoal decreased the serum half-life of phenobarbital from 110 .+-. 8 to 45 .+-. 6 h (P < 0.01), increased the total body clearance of phenobarbital from 4.4 .+-. 0.2 to 12.0 .+-. 1.6 ml/kg per h (P < 0.01) and increased the nonrenal clearance from 52 to 80% of the total body clearance. Evidently, oral administration of activated charcoal enhances the nonrenal cleareance of phenobarbital.