Therapeutic drug monitoring of carbamazepine and valproic acid: interindividual variability in epilepsy patients

Aims: Epilepsy is a chronic neurological disorder affecting 1-3% of the global population, characterized by recurrent seizures. Monitoring blood levels of valproic acid and carbamazepine, two commonly used antiepileptic drugs, is essential for effective seizure control. This study aims to analyze the serum concentrations, demographic characteristics and concomitant drug use of patients treated with valproic acid or carbamazepine. Methods: This retrospective study was conducted at Kırklareli Training and Research Hospital, analyzing the medical records of epilepsy patients treated with valproic acid or carbamazepine. Medical records of 440 epilepsy patients were retrospectively analyzed. Demographic data, concurrent medication use and blood drug levels were recorded, and rates of achieving therapeutic levels were compared. Results: Of the 440 patients, 378 were treated with valproic acid, and 62 with carbamazepine. In the valproic acid group, 62.2% reached therapeutic levels, with an average concentration of 68.15 µg/ml. In the carbamazepine group, only 27.4% reached therapeutic levels, with an average of 10.07 µg/ml. A statistically significant difference was found between the two groups. A significant association was found between drug interaction counts and non-therapeutic levels in the carbamazepine group (p