Efficacy and Blood Levels of Lacosamide in Patients with Focal Epilepsy

Objectives: The aim was to analyze clinical targets for lacosamide (LCM) blood levels in patients with focal epilepsy. Referring to the LCM optimal range will motivate us to think about the importance and usefulness of measuring its blood levels. Methods: A total of 101 patients (45 females, 56 males) were treated with LCM. Blood sampling was done 1 month after the start of oral medication (the levels reached steady state) if the LCM treatment had been continued and then 6 and 12 months after. The efficacy of LCM was evaluated by the reduction in the epileptic seizure rate (RR) at the time of blood sampling. The patients were classified as effective cases (seizure reduction rate ≥ 50%) and ineffective cases (< 50%). The actual level, the calculated peak/trough levels, and the levels for each type of seizure were investigated. Statistical analysis was performed using Spearman’s rank correlation coefficient and the Wilcoxon signed-rank test. Results: A positive correlation was seen between blood levels and dosage (r = 0.446). However, the blood levels and RR showed no correlation. The blood levels were higher in effective cases than in ineffective cases at all time points (measurement P < 0.001, peak P = 0.013, trough P = 0.001). Because the range was set so that the effective and ineffective groups did not overlap, the optimal range of LCM was found to be 8.0–10.5 µg/mL. Conclusions: Measuring and calculating blood levels of LCM and adjusting the dosage to reach the optimal range are recommended. Moreover, the optimal range for LCM was determined as a therapeutic target.