Little is known about pregnancy-induced alterations in the pharmacokinetics of the newer antiepileptic drugs, especially when used in combinations. Two women receiving combination therapy of lamotrigine (LTG) and oxcarbazepine (OXC) were followed prospectively during pregnancy and puerperium. Steady-state concentrations of LTG and the active metabolite of OXC, 10-hydroxycarbazepine (MHD), were measured at regular intervals using a dried blood spot method, and clearances were calculated. A strong effect of pregnancy on the clearance of both LTG and MHD was seen. An increase in seizure frequency occurred in both women. This stresses the importance of therapeutic drug monitoring of LTG and MHD during pregnancy. In case of breakthrough seizures or increased seizure frequency, dosage adjustment of both drugs may be required.
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