A Note on Therapeutic Equivalence and Therapeutic Ratio with Application to Studies in Respiratory Diseases


This paper argues that the concepts of therapeutic equivalence and noninferiority trials have some unclear logic and give results that might not be in accordance with clinical experience. They are also totally unnecessary. The discussion focuses on therapeutic equivalence trials, but carries over directly to noninferiority trials. Therapeutic equivalence proves to be a flexible tool for delusion and should be abandoned. Statistics should end where it can claim to be correct and useful, in this case, with estimates and confidence limits of clinically relevant parameters such as relative dose potency. If therapeutic equivalence is still needed for special purposes, the testing and definition should be done on the dose scale.

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Correspondence to Anders Källén.

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Källén, A. A Note on Therapeutic Equivalence and Therapeutic Ratio with Application to Studies in Respiratory Diseases. Ther Innov Regul Sci 35, 1495–1505 (2001). https://doi.org/10.1177/009286150103500444

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Key Words

  • Therapeutic equivalence
  • Noninferiority trials
  • Therapeutic ratio