Comparison of alternative outcome measures for antiepileptic drug trials

Studies to determine the efficacy of antiepileptic drugs often use seizure frequency as an outcome measure. Time to kth seizure (k up to 12) was investigated as an alternative endpoint. Monte Carlo simulations, based on seizure behavior in previous clinical trials, were used to evaluate crossover studies with these endpoints. exhibited the highest power. However, tests on time to the 12th seizure, for a sample size of 50, approached the power of tests on seizure frequency with a sample size of 20. Including patients with less severe epilepsy (two vs four seizures per month) did not change the power of tests on time to the kth seizure and lowered it only moderately for tests on seizure frequency. The simulation methodology presented can be adapted to evaluate other design variations.