Effect of Charcoal and SorbitolCharcoal Suspension on the Elimination of Intravenous Phenobarbital

The effects of two different oral charcoal suspensions on the elimination of a 200 mg/70 kg, 1 h intravenous (i.v.) infusion of phenobarbital and the tolerances of the two regimens were determined in a randomized crossover study in six healthy male volunteers. Phenobarbital was given i.v. alone or together with 105 g of oral activated charcoal suspension or with 105 g of a commercially available sorbitol-charcoal suspension over a 36-h period. A 13–34 decrease in the area under the serum concentration time curve (AUC) for 0–60 h occurred with the administration of the activated charcoal, and a 19–52 decrease occurred with the commercial sorbitol-charcoal regimen. The mean apparent systemic clearance of total phenobarbital increased from 0.089 ± 0.019 ml/min/kg to 0.141 ± 0.029 and 0.146 ± 0.036 ml/min/kg with the charcoal and sorbitol-charcoal treatments, respectively. No significant change in the fraction of phenobarbital bound to protein was detected. The charcoal regimen caused constipation in one subject. All subjects taking the sorbitol-charcoal preparation experienced diarrhea: there were no changes in electrolytes with either charcoal suspension. All subjects preferred the sorbitol-charcoal preparation.