Bioavailability and Bioequivalence

Bioavailability and bioequivalence assessments of formulations are components of the marketing authorization/approval process for drug products. New Drug Applications (NDAs) of innovator drugs typically include bioavailability and bioequivalence testing, while Abbreviated New Drug Applications (ANDAs) of generic drugs typically include bioequivalence testing. After approval, innovator and generic drugs rely on bioequivalence testing to assure on-going product quality when manufacturing changes occur. Bioavailability and bioequivalence focus on the release of the drug substance from a drug product, and the subsequent absorption into the systemic circulation. Therefore, bioequivalence approaches generally follow approaches for bioavailability. The purpose of establishing bioequivalence is to demonstrate equivalence in biopharmaceutics quality between the proposed and existing drug product (e.g. generic versus brand; post-change versus pre-change product). Therefore, bioequivalence testing typically eliminates the need for preclinical tests and clinical trials. The basic principles and approaches of evaluating bioavailability and bioequivalence are discussed.