Topiramate: as monotherapy in newly diagnosed epilepsy

Topiramate is an antiepileptic drug that has a broad spectrum of antiseizure effects, which appear to be the result of several neurostabilising pharmacological mechanisms. These include blockade of ion channels, potentiation of GABA neuroinhibition and glutamate receptor antagonism at non-NMDA receptors, as well as mild inhibition of carbonic anhydrase. Topiramate monotherapy dose dependently reduced the number of patients who met seizure related exit criteria in children (aged > or =6 years) and adults with epilepsy. This effect was also observed in patients who had previously experienced partial onset seizures and for those who had experienced generalised tonic clonic seizures. Six-month and 1-year seizure-free rates were dose-dependently reduced. In epilepsy, topiramate monotherapy 100 or 200 mg/day was as effective as carbamazepine 600 mg/day or valproate 1250 mg/day as measured by time to study exit for any reason, time to first seizure and percentage of patients seizure-free in the final 6 months of treatment (mean treatment duration 244 days). Adverse events associated with topiramate monotherapy that were dosage related included paraesthesia, weight loss and diarrhoea. Renal calculi were also reported in both fully published trials.