Single dose pharmacokinetics of carbamazepine-10,11-epoxide in patients on lamotrigine monotherapy

The pharmacokinetics of a single oral dose of carbamazepine-10,11-epoxide (CBZ-E, 100 mg) were compared in 10 patients on chronic monotherapy with lamotrigine (LTG, 200-300 mg/day) and in 10 drug-free healthy control subjects. CBZ-E pharmacokinetic parameters in LTG-treated patients were found to be similar to those observed in controls (half-life: 7.2 +/- 1.6 vs 6.1 +/- 0.9 h; apparent oral clearance: 110.8 +/- 53.1 vs 120.5 +/- 29.9 ml/h/kg; apparent volume of distribution: 1.08 +/- 0.37 vs 1.04 +/- 0.25 l/kg respectively; means +/- s.d.). These data indicate that, contrary to previous suggestions, LTG has no effect on the metabolic disposition of CBZ-E