A Decision-Theoretical Perspective on Bioequivalence

Bioequivalence is a term used for the property of two treatments, formulations, or medical products (henceforth treatments) that their effects in a specified population are identical, or that the treatments can be interchanged without any differential therapeutic impact. In most contexts, ‘identical’ is qualified by ‘for all intents and purposes’, is acknowledged to mean ‘similar’, or is meant to be interpreted as such. In established approaches, providing evidence of bioequivalence amounts to rejecting the hypothesis that the difference of the average effects of the two treatments, Δ, is distant from zero-that the two-average treatment effects are dissimilar. A study to provide such evidence should start by defining the borderline between similar and dissimilar. It comprises a positive and a negative value, Δ+ > 0 and Δ< 0, or the interval they delimit, which contains zero. If we knew that the treatment effect is within this interval we would declare bioequivalence (B), and would declare dissimilarity (D) otherwise. Setting both δ and δ to zero corresponds to a dichotomy that is false because with such a degenerate borderline it would be safe to conclude that bioequivalence is absent. After all, there are uncountably many alternatives to the exact zero, and uncountably many of them are arbitrarily close to zero [1].