Carbamazepine Plasma Concentration: Relationship to Cognitive Impairment

• Neuropsychological function was assessed before and after carbamazepine monotherapy in children with newly diagnosed complex partial epilepsy. Simultaneous video-electroencephalographic monitoring examined the influence of subclinical abnormal electrical discharges on performance. Total and unbound plasma carbamazepine concentrations were examined in relation to changes in performance at low (carbamazepine level, ≤32 μmol/L [≤7.5 mg/L]) and moderate (carbamazepine level, >34 μmol/L [>8.0 mg/L]) drug levels. The data suggest a mild beneficial effect of carbamazepine on speeded eye-hand coordination and, at low drug levels, more rapid processing of items in memory. Efficiency of learning new information and memory-scanning rate displayed a concentration-dependent relationship with carbamazepine level, with poor performance significantly associated with higher carbamazepine plasma concentrations. Carbamazepine free levels were equivalent to total levels in predicting cognitive side effects.