Interaction of topiramate with carbamazepine: Two case reports and a review of clinical experience

Abstract

We describe a possible clinical interaction between topiramate (TPM) and carbamazepine modified release (CBZ-MR) in patients taking maximum tolerated doses of carbamazepine. Data are presented on 25 patients who contacted the epilepsy nurse specialist telephone helpline for advice after starting treatment with TPM. Thirteen male and 12 female patients, mean age 41 years (range 25-69 years), with localization-related epilepsy contacted the helplines, between November 1999 and March 2001, complaining of symptoms of antiepileptic drug intoxication after starting treatment with TPM. All were taking maximum tolerated doses of CBZ-MR before starting TPM. Sixteen of the patients were taking other antiepileptic drugs concomitantly with CBZ-MR and TPM. Symptoms of intoxication were similar to those previously experienced when maximum tolerated doses of CBZ-MR were exceeded. Symptoms resolved when concomitant CBZ-MR doses were reduced, enabling further dose escalation of TPM. To our knowledge, neither clinical nor pharmacological interactions between CBZ and TPM have been described previously in man. These data suggest that such an interaction may be of clinical importance, and that reduction of the CBZ dose may enable optimization of the dose of TPM, improving seizure control. © 2002 BEA Trading Ltd. Published by Elsevier Science Ltd. All rights reserved.