Pharmacokinetics of lamotrigine in children in the absence of other antiepileptic drugs.

We evaluated the pharmacokinetics of lamotrigine in 12 children with epilepsy who were receiving no other antiepileptic drugs. Each patient received a single oral dose of lamotrigine 2 mg/kg. Plasma concentrations of the drug were measured up to 48 hours after dosing. Pharmacokinetic parameters were calculated using noncompartmental methods. After rapid absorption, the lamotrigine concentration declined monoexponentially. Oral clearance was 0.64 +/- 0.26 ml/min/kg. The apparent volume of distribution was 1.50 +/- 0.51 L/kg. Weight-normalized clearance and volume were higher in children than in adults. The mean half-life was 32 hours, similar to that in adults. Should similar plasma lamotrigine concentrations in adults and children be desirable, children will likely require higher weight-normalized doses at the same dosing frequency.