Enhancement of phenytoin elimination by multiple-dose activated charcoal

The effect of multiple-dose activated charcoal on the elimination of intravenously administered phenytoin was studied. Seven normal volunteers received phenytoin sodium 15 mg/kg IV with and without activated charcoal. During the charcoal phase, a total dose of 300 g was administered in repeated doses over 48 hours with sufficient sorbitol to produce one to two bowel movements per day. Serum phenytoin concentrations were determined from one to 72 hours after the infusions and were fitted to a one-compartment linear elimination model. The administration of multiple-dose activated charcoal reduced the phenytoin half-life from 44.5 to 22.3 hours. In addition, phenytoin area under the curve was decreased and the elimination rate was increased. Multiple-dose activated charcoal is effective in enhancing the elimination of phenytoin in normal volunteers. Although future studies are needed to determine its role in treating patients with phenytoin toxicity, multiple-dose activated charcoal may provide a readily available, inexpensive therapeutic intervention.