Clinical efficacy and pharmacokinetics of lamotrigine for childhood-onset intractable epilepsy

Objective: We investigated the clinical efficacy and pharmacokinetics of lamotrigine (LTG) as an add-on therapy in childhood-onset intractable epilepsy. Methods: We reviewed the charts of 28 outpatients who had received LTG as an add-on therapy. The data collected included epilepsy type, seizure frequency, concomitant anti-epileptic drugs, dosage of LTG and LTG serum levels. Furthermore, we reviewed the relationship between the LTG serum levels (μg/ml) and dosage of LTG (mg/kg/day), as well as the relationship between the LTG serum levels (μg/ml) and clinical efficacy in the following 2 groups: the valproate sodium (VPA) combination group and the non-VPA combination group. Results: A reduction of 50% or more in seizure frequency was observed in 10 patients. In addition, there was a high correlation between the LTG serum levels and the dosage of LTG in each group. In the VPA combination group, the average of LTG serum levels in patients with adequate therapeutic response (50% reduction in seizure frequency) was higher than that in patients without adequate therapeutic response. In the non-VPA combination group, the average LTG serum level in adequate response patients was lower than that in patients without adequate therapeutic response. However, the epilepsy types of adequate response patients differed in the two groups. Conclusions: The LTG serum level is predictable based on the dosage of LTG. It was judged that the effective blood concentration of LTG differed when used with VPA, although factors other than the combined use of VPA should have been taken into consideration also.