Bioequivalence - a DRUG that has the same biological effect in the body as a substance the body makes naturally (such as a HORMONE supplement) or two or more drugs that have the same BIOAVAILABILITY and EFFICACY. Bioequivalence is a significant concern with NARROW THERAPEUTIC INDEX (NTI) drugs, which require precise and consistent dosing, as well as with generic drugs.
A GENERIC DRUG, which is a different chemical formulation of equivalent active ingredients compared to the innovator (original) drug, is not necessarily bioequivalent to the INNOVATOR DRUG. That is, the same drug product from different manufacturers may contain the same amounts of active ingredient though not the same inactive ingredients or different proportions of inactive ingredients. The extent to which these differences influence bioavailability (the amount of the active ingredient that enters the body) varies among classifications of drugs and is especially crucial with NTI drugs.
The US Food and Drug Administration (FDA) establishes and regulates the parameters of bioequivalence. Drugs that are bioequivalent must fall within a specific range for the amount of time it takes for each drug to enter and remain in the BLOOD circulation.