Effect of oral activated charcoal on propranolol pharmacokinetics following intravenous administration to rabbits

The pharmacokinetics of propranolol following intravenous administration (1 mg/kg), with and without treatment with oral activated charcoal, was investigated in rabbits. In charcoal-treated rabbits a significant reduction in propranolol serum concentrations was observed compared to control animals. Charcoal treatment significantly reduced the half-life of elimination (16.6%) and the mean residence time (19%) of propranolol. A 17% increase in the systemic clearance and a 14% decrease in AUC were also noted. Charcoal administration did not significantly alter the volume of distribution (Vc' V(area) and Vss) or the apparent distribution half-life. A two-compartment model adequately described propranolol in control and treated rabbits. The results indicate that administration of oral activated charcoal enhances the systemic elimination of propranolol. This is presumably mediated by interruption of the enterohepatic circulation of propranolol by activated charcoal.