Multiple-dose activated charcoal compared to urinary alkalinization for the enhancement of phenobarbital elimination

Urinary alkalinization and multiple-dose activated charcoal are modalities advocated for the enhancement of phenobarbital elimination in poisoned patients. However, no studies exist comparing the efficacy of these two means of elimination enhancement. We compared their effects on the pharmacokinetic disposition of intravenously administered phenobarbital.

Ten healthy volunteers participated in each of three randomly ordered study phases. During each phase, 5 mg of intravenous phenobarbital per kilogram of body weight was administered. During phase I, no interventions were made in attempt to enhance phenobarbital elimination. In phase II, participants underwent 24 hours of urinary alkalinization. Throughout phase III, volunteers received six doses of activated charcoal and two doses of sorbitol over 24 hours.

The phenobarbital elimination half-life was 148 hours, 47 hours and 19 hours during the control, alkalinization and charcoal phases, respectively. Statistically significant differences in the elimination of phenobarbital were detected when each of the following phases were compared: I vs II, I vs III and II vs III.

Both urinary alkalinization and multiple doses of activated charcoal are effective for the enhancement of phenobarbital elimination but multiple-dose charcoal was superior to urinary alkalinization in our study population.