Clinical Response and Serum Concentrations in Low-Dose Lacosamide Monotherapy for Children With Paroxysmal...

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by brief, movement-triggered attacks. Voltage-gated sodium channel-blocking antiseizure medications, such as carbamazepine, although commonly used to treat PKD, have limitations in children due to enzyme induction and adverse effects. Lacosamide (LCM) enhances the slow inactivation of voltage-gated sodium channels; however, its efficacy and tolerability are unknown in children with PKD. Therefore, this study evaluated the clinical course of low-dose LCM monotherapy and associated serum concentrations for PKD.

We retrospectively reviewed records of five patients with PKD treated with LCM monotherapy at Saitama Children's Medical Center between August 2016 and July 2025. Data included age at LCM initiation, pretreatment attack frequency, LCM dose, serum LCM concentrations, treatment response, and adverse events. The primary outcome was the duration to attack remission or reduction, evaluated at 6 months.

The median age at LCM initiation was 13.9 (range, 11.4-15.4) years. Attack frequency before treatment was ≥10, 5-10, and 1-5 episodes/day in two, two, and one patient, respectively. The median initial and maintenance doses were 2.0 and 1.9 mg/kg/day, respectively. Attacks disappeared within 2 days in four patients and decreased by 80% within 6 days in one. All patients achieved complete remission by 6 months. In all patients, attacks recurred after discontinuation but resolved within one day of treatment resumption. Serum LCM trough concentrations during maintenance therapy were 1.1-4.1 μg/mL. No adverse events were documented.

Low-dose LCM monotherapy was associated with rapid control of PKD and remission at low serum concentrations, suggesting its clinical potential.