Effect of vigabatrin addition on carbamazepine blood serum levels in patients with epilepsy

Because vigabatrin (VGB) is not metabolized by liver enzymes and does not b ind with serum proteins, there is little theoretical chance of it interacti ng with other antiepileptic drugs. However, our observations have shown tha t if VGB is added to carbamazepine (CBZ) monotherapy, some patients respond with adverse, toxic symptoms suggesting possible carbamazepine-vigabatrin interaction. This article presents the results of a study of 66 epileptic p atients (27 women and 39 men), age 10-66 Sears (mean, 28.2 years), with foc al seizure onset with or without secondary generalization. In these patient s, in addition to CBZ therapy with an average dose of 16.7 mg/kg per day (8 .6-26.8), VGB, average dose 31.1 mg/kg per day (7.1-57.9), was added. CBZ c oncentration was measured twice: prior to VGB introduction and 5-12 weeks a fter the final dose of VGB was reached. In our study 69.7% of patients resp onded to VGB addition with a significant increase (by at least 10%) in CBZ concentration. A correlation between the value of the increase and the init ial level of CBZ prior to VGB addition was found also. Correlational analys is (Pearson's r) revealed a negative correlation between CBZ concentration and increased concentration after VGB addition (r = -0.47, df = 64, P < 0.0 01). This negative correlation means that if the initial CBZ level is lower , its concentration value after VGB addition is higher. (C) 2000 Elsevier S cience B.V. All rights reserved.