THE PHARMACOKINETICS OF OXCARBAZEPINE AND ITS ACTIVE METABOLITE 10-HYDROXY-CARBAZEPINE IN HEALTHY-SUBJECTS AND IN EPILEPTIC PATIENTS TREATED WITH PHENOBARBITONE OR VALPROIC ACID

The kinetics of oxcarbazepine (OXC) and its active metabolite 10-hydro xy-carbazepine (10-OH-CZ) after a single oral OXC dose (600 mg) were c ompared in healthy control subjects and in epileptic patients treated with phenobarbitone or sodium valproate (n = 8 in each group). In all groups, serum 10-OH-CZ concentrations were much higher than those of t he parent drug. In patients on valproate, the kinetics of OXC and 10-O H-CZ did not differ significantly from those observed in controls. In patients on phenobarbitone, AUC values of both OXC and 10-OH-CZ were l ower than in controls (2.9 +/- 0.4 vs 5.1 +/-0.7 mug ml-1 h and 89 +/- 7 vs 119 +/- 10 mug ml-1 h respectively, means +/- s.e. mean, P < 0.0 5), whereas 10-OH-CZ half-lives were only marginally shorter (17 +/- 1 h vs 20 +/- 2 h, NS). These data indicate that the biotransformation of OXC and 10-OH-CZ may be accelerated by concomitant treatment with p henobarbitone but that the magnitude of this effect is unlikely to be of great clinical significance.