Bioavailability is a measurement of the rate and extent (amount) to which the active ingredient or active moiety becomes available at the site of action. Bioavailability is also considered a measure of the rate and extent of therapeutically active drug that is systemically absorbed. For drug products that are not intended to be absorbed into the bloodstream, bioavailability may be assessed by measurements intended to reflect the rate and extent to which the active ingredient or active moiety becomes available at the site of action.
A generic drug product is considered bioequivalent to the reference listed drug (RLD) product if both products are pharmaceutical equivalents and the generic drug product’s rate and extent of systemic drug absorption (bioavailability) do not show a statistically significant difference when administered in the same molar dose of the active ingredient, in the same chemical form, in a similar dosage form, by the same route of administration, and under the same experimental conditions. The RLD is generally the brand product.
- The generic drug product requires an abbreviated new drug application (ANDA) for approval by the U.S. Food and Drug Administration (FDA) and may be marketed after patent expiration of the reference drug product.
- The reference listed drug product is usually the currently marketed, brand-name product with a full new drug application (NDA) approved by the FDA. The RLD is the reference drug product identified by FDA (Electronic Orange Book).