A group sequential approach to crossover trials for average bioequivalence.

Group sequential methods to allow the possibility of early termination of a trial due to sufficiently convincing results are a standard in therapeutic clinical trials but have been little considered in bioequivalence trials. We investigate the statistical properties of one group sequential approach to bioequivalence trials. In particular, we are interested in maintenance of level (5%), quantification of any loss of power, and the probability of early stopping. These properties are assessed via data simulated according to a pharmacokinetic model. We find that there are cases where a group sequential approach has a substantial probability of early stopping, with essentially no loss of power.