Clinical impact of the dose and blood concentration of lacosamide in Japanese pediatric patients with epilepsy: A cohort study.

Purpose: The relationship between treatment efficacy/tolerability and the dose/blood concentration of lacosamide (LCM) was investigated in a clinical cohort of Japanese pediatric patients with epilepsy.

Methods: This retrospective analysis reviewed the medical records of patients treated with LCM for >6 months at the Department of Pediatrics, Hiroshima University Hospital, from September 2017 to January 2021. The collected data included age, sex, epilepsy type, seizure type, seizure frequency before and after treatment initiation, adverse events leading to LCM discontinuation, dose at any evaluation point, serum concentration, and concomitant antiepileptic drugs (AEDs).

Results: The study included 51 patients (31 male patients) between the ages of 2 and 19 years. All patients were Japanese. Epilepsy was classified as focal in 44 patients, generalized in six patients, and combined generalized and focal in one patient. The 50% responder rate for LCM treatment was 56.9%. Seven patients experienced complete seizure control (absence of seizures for 6 months before the follow-up visit). A relationship between dose and blood concentration was identified. Although the blood LCM concentration was higher in the responders than in the nonresponders (7.86 vs. 6.16 μg/mL; p = 0.028), there was no significant difference in dose between the two groups. Lacosamide showed efficacy at a dose >5 mg/kg/day in more than half of the 50% responders. The treatment-emergent adverse events (TEAEs) included seizure aggravation in five patients, irritability in two patients, and somnolence and drug eruption in one patient each. In six patients with TEAEs, the TEAEs developed within 1 month after treatment initiation and led to LCM discontinuation.

Conclusion: In Japanese pediatric patients with epilepsy, LCM treatment is effective, particularly at higher doses. The blood concentration may be related more to efficacy than to dose. Lacosamide is generally well-tolerated by pediatric patients, and should be used at the maximum tolerable dose (needed to be gradually increased) in patients with otherwise insufficient seizure control. As TEAEs leading to discontinue treatment likely occur in early phase, it is needed to monitor patients carefully if TEAEs would happen in that phase.