Abstracts

RATIONALE: Reporting efficacy data after long-term exposure of an AED can be done using different methods which greatly influence the reported results. We present the data from the levetiracetam (LEV) development program as an example of the different methods used in calculating seizure-free rates. As of June 1999, 1422 patients had been exposed to LEV, with 1052 exposed for at least 6 months, 826 exposed for at least 1 year, and 562 still on LEV at time of review. METHODS: In examining seizure-free rates, the duration of seizure freedom and the population studied needs to be clearly defined. We compare duration of seizure freedom (6 months vs. 1 year) in various populations (intent to treat, at least 1 year exposure, or patients presently using LEV). RESULTS: 183 patients achieved seizure freedom for at least 6 months and 109 for at least one year. CONCLUSIONS: LEV has a significant incidence of seizure freedom (8-33%) in this refractory population. The results are markedly impacted by the method used to define seizure freedom. A consistent methodology for calculating seizure-free rates is needed to assure equitable comparisons between various anti-epileptic therapies.