Active control equivalence trials: some methodological aspects.

The therapeutic efficacy of an investigational new drug is best demonstrated in clinical trials against a placebo control. However, ethical requirements increasingly preclude the use of an inactive control substance as a treatment alternative, as clinical testing to compare the effects of active treatments, has become more frequent. The statistical evaluation and interpretation of these trials is complex and requires the demonstration of 'equivalence' or 'at-least equivalence' between the experimental drug and a comparable standard therapy. The design of controlled clinical trials to compare the effects of moclobemide, a new and selective monoamine oxidase-A inhibitor, with those of standard tricyclic antidepressant drugs involved the refinement of selection strategies, formulation of hypotheses, means of statistical analysis and clinical interpretation.