SEQUENTIAL DESIGNS FOR EQUIVALENCE STUDIES

Sequential designs are increasingly being used in major clinical trial s concerning life-threatening diseases. So far most applications have concerned trials designed to establish whether an experimental treatme nt is superior to a control. However, many trials are conducted with t he objective of showing that an experimental treatment is equivalent t o a control. This paper concerns the application of sequential designs to equivalence trials. Criteria for claiming equivalence are reviewed and compared, and methods first developed in the context of bioequiva lence are described. Appropriate sequential procedures are identified. A simulated example, based on a clinical comparison of bronchodilator s, is used to illustrate both the double triangular test and a compara ble procedure constructed from alpha-spending functions.