Following a protocol amendment, this study resumed recruitment from April 10 to September 4, 2009. This is a randomized, double-blind, parallel-group, active-comparator, multi-center study. The study consists of 5 phases: pretreatment (screening), double-blind titration phase, double blind maintenance phase, a transition phase, and an open-label phase. Patients who are not eligible or choose not to enter the transition and open-label phases of the study will complete an exit phase following double-blind treatment.The primary outcome variable is long term retention rate and safety of adjunctive therapy with carisbamate vs. topiramate and levetiracetam over a six month period. This primary endpoint is a clinically meaningful measure of efficacy, safety and tolerability over time, reflecting the therapeutic effectiveness of antiepileptic drugs (AEDs). Safety evaluations including adverse event monitoring, blood tests, and vital signs will be conducted throughout the study.The hypothesis is that the 3 study medications at a minimum will have similar treatment retention rates, but based on their distinct efficacy and side effect profiles, will have discernible differences in the rates of selected adverse events and reasons for treatment discontinuation in patients with partial onset siezures. Patients must be on at least 1, but not more than 2, baseline AEDs for 30 days prior to screening. By end of week 8 patients must have reached the following minimum dosages of study drug to be permitted to continue: carisbamate 400 mg/day, topiramate 200 mg/day, or levetiracetam 1000 mg/day. Double-blind phases last approximately 12 months. Carisbamate 800 mg/day, topiramate 300 mg/day and levetiracetam 2000mg/day will be administered orally in two equally divided doses.
The purpose of this research study is to compare the long term effectiveness, safety and tolerability of carisbamate compared to two other frequently prescribed anti-epileptic drugs (AEDs) in patients with epilepsy.