Pharmacokinetic interaction between albendazole sulfoxide enantiomers and antiepileptic drugs in patients with neurocysticercosis

The aim of the present investigation was to determine the interaction between the antiepileptic drugs (AEDs) phenytoin, carbamazepine, and phenobarbital and the enantioselective metabolism of albendazole. Thirty-two adults with a diagnosis of the active form of intraparenchymatous neurocysticercosis and treated with albendazole at the dose of 7.5 mg/kg every 12 hours for 8 days were studied. The patients were divided into four groups based on the combined use of AEDs or not: control group (n=9), phenytoin group (n=9 patients treated with 3-4 mg/kg/d sodium phenytoin), carbamazepine group (n=9 patients treated with 10-20 mg/kg/d carbamazepine), and phenobarbital group (n=5 patients treated with 1.5-4.5 mg/kg/d phenobarbital). Serial blood collections were carried out on day 8 of albendazole treatment during the last 12-hour dose interval. Plasma concentrations of the (+)- and (-)-albendazole sulfoxide (ASOX) and albendazole sulfone (ASON) metabolites were determined by high-performance liquid chromatography using a chiral phase column and fluorescence detection. The pharmacokinetic parameters were analyzed by analysis of variance followed by the Tukey-Kramer test. The results are reported as means. The following differences (P<0.05) were observed between the control and the phenytoin. carbamazepine, and phenobarbital groups, respectively: (+)-ASOX area under the concentration-time curve for 0 to 12 hours after treatment (AUC(0-12)) 6.1, 2.1, 3.1, 2.4 mu g/h/mL; (+)-ASOX maximum plasma concentration (C-max) 0.8, 0.3, 0.4, 0.3 mu g/mL; (+)-ASOX half-life (t(1/2)) 8.0, 3.8, 4.1, 4.9 h; (-)-ASOX AUC(0-12) 1.8, 0.4, 0.6, 0.5 mu g/h/mL; (-)-ASOX C-max 0.2, 0.06, 0.1, 0.1 mu g/mL; (-)-ASOX t(1/2) 4.3, 1.9, 2.2, 2.1 h; ASON AUC(0-12) 0.5, 0.2 mu g/mL; ASON C-max 0.8, 0.3, 0.4, 0.3 mu g/mL; ASON t(1/2) 8.0, 3.8, 4.1 It. The results show that phenytoin, carbamazepine, and phenobarbital induce to approximately the same extent the oxidative metabolism of albendazole in a nonenantioselective manner. Notably, a significant reduction in the plasma concentration of the active ASOX metabolite was observed in patients with neurocysticercosis treated with these AEDs.