Pharmacokinetic variability of eslicarbazepine in real clinical practice

•Eslicarbazepine metabolite licarbazepine serum levels in patients treated with eslicarbazepine acetate in real clinical practice have a linear correlation with the dose administered.•Eslicarbazepine therapeutic drug monitoring may be useful to assess adherence to treatment and to adjust the dose in a personalized manner. Eslicarbazepine acetate (ESL) is a sodium channel blocker indicated for partial-onset seizures with or without secondary generalization, at a single daily dose. There are very few publications on the levels of ESL metabolites in real clinical practice. To describe the serum levels of licarbazepine (main metabolite of ESL) in patients with refractory epilepsy in real clinical practice. To evaluate the influence of age, sex, and polytherapy on levels and adverse effects. This study involved a retrospective analysis of patients diagnosed with epilepsy treated with ESL for whom plasma levels of licarbazepine were available, measured by spectrophotometry. Sixty-four patients were included. One patient had licarbazepine levels of 0 (admitted not taking the drug) was not analyzed. Mean licarbazepine levels of 7.66 µg/mL (400 mg/day dose), 16.56 µg/mL (800-mg dose), and 20.80 µg/mL (1200 mg) were significantly different. There was a significant correlation between daily dose and serum levels (p