Effect of comedication on lamotrigine clearance in Korean epilepsy patients.

Abstract Background Lamotrigine (LTG) is a widely used antiepileptic-drug (AED) for the treatment of epilepsy. We investigated the effect of AED comedication on LTG clearance in Korean patients with epilepsy. Methods The authors reviewed the medical charts for all patients ≥ 18 years who have received LTG as monotherapy or adjunctive therapy. Data collected included LTG levels, dosage, treatment duration, concomitant AEDs and specific side effects. LTG clearance was estimated according to comedication. Results A total of 580 blood samples from 548 patients were analyzed. LTG clearance in the enzyme-inducing AED (EIAED) coadministration group was the highest (0.050 l/kg/h), followed by the LTG monotherapy group (0.028 l/kg/h), the coadministration group of both valproate (VPA) and EIAED (0.024 l/kg/h) and the VPA coadministration group (0.018 l/kg/h). When LTG was administered with both VPA and EIAED, the multiple EIAED group had higher LTG clearance than the single EIAED group. Conclusions Concomitant administration of valproate reduced LTG clearance by approximately 35%, while EIAEDs increased LTG clearance by 80%. These relationships indicate the importance of considering the effects of comedication on LTG clearance when determining LTG dosage.