The efficacy of levetiracetam for focal seizures and its blood levels in children

Aim: To evaluate the efficacy of levetiracetam (LEV) and the usefulness of measurement of its blood levels during the follow-up of patients with focal seizures. Methods: Twenty-four patients (13 cases without impairment of consciousness or awareness and 11 cases with them or evolving to a bilateral, convulsive seizure) treated with LEV had their peak blood levels measured. The blood concentrations were measured at 2 weeks, 1 year and 2 years after reaching the LEV maintenance dosage. The efficacy of LEV was evaluated with repeated blood sampling to determine the seizure reduction rate. The patients were classified as effective cases (seizure reduction rate > 50%) and ineffective cases (<= 50%). Results: In Japanese children treated with LEV, the dosage and blood level showed positive correlations. The blood levels were higher in effective cases than in ineffective cases at all time points (p < 0.05). In effective cases, the blood concentration was 23.26 +/- 6.88 mu g/mL (mean +/- SD) 2 weeks later, 23.59 +/- 8.23 mu m/mL 1 year later, and 24.46 +/- 7.57 mu g/mL 2 years later. However, the blood levels and efficacies showed positive correlations only at 2 weeks and 1 year later. No patients had any side effects. Conclusions: No precise definition of the therapeutic range was possible because of the incomplete correlation between the blood level and seizure frequency. Instead of a therapeutic range, we recommend an optimal range for LEV of 20-30 mu g/mL as a therapeutic target without any side effects. (C) 2014 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.