Optimal Perampanel Blood Level Based on the Correlation between The Efficacy and Blood Concentration in Patients with Focal Epilepsy

Abstract

Objective: To evaluate the efficacy of perampanel (PER) over a period of 2 years and the usefulness of measuring blood levels during follow-up for patients with focal epilepsy.
Methods: A total of 46 patients with focal epilepsy (mean age: 24.7±9.3 years) were identified from medical records and their peak blood PER levels were measured. Of the 46 patients, 18 used enzyme inducers (carbamazepine, phenobarbital, phenytoin and topiramate) in combination with PER. Blood PER levels were measured immediately after reaching the PER maintenance dosage and 6 months, 1, 1.5, and 2 years later. The efficacy of PER was evaluated at the same time points as the blood sampling to determine the seizure reduction rate. The cases were then classified as effective (mean seizure reduction rates ≧50%) or ineffective (＜50%).
Results: The dosage and blood PER levels showed a positive correlation in cases of combination use without an inducer (r=0.388). However, no correlations were seen in all patients or in cases of combination use with an inducer (r=0.247, 0.326, respectively). In several groups, there was no positive correlations were seen between blood PER levels and efficacy. In all patients and cases of combination use with an inducer, significant differences were seen in the blood PER levels of effective vs. ineffective cases (p=0.041, 0.007, respectively). The optimal range was 500–530 ng/mL based on the mean and standard deviation in the effective cases. In the case of combination use, the range was 420–600 ng/mL.
Conclusion: We recommend an optimal range of PER as a therapeutic target as 500–600 ng/mL. Because this range is the common range of all patients and cases of combination use with an inducer.