ABSTRACT
Defined as relative bioavailability (BA), bioequivalence (BE) involves comparison between a test
(T) and reference (R) drug product, where Tand R can vary, depending on the comparison to be
performed (e.g., to-be-marketeddosage formvs. clinical trialmaterial, generic drugvs. reference
listed drug, drug product changed after approval vs. drug product before the change). Although
BA and BE are closely related, BE comparisons normally rely on (i) a criterion, (ii) a confidence
interval for the criterion, and (iii) a predeterminedBE limit. BE comparisons could also beused in
certain pharmaceutical product line extensions, such as additional strengths, new dosage forms
(e.g., changes from immediate release to extended release), and new routes of administration. In
these settings, the approaches described in this guidance can be used to determine BE. The
general approaches discussed in this guidance may also be useful when assessing pharma-
ceutical equivalence or performing equivalence comparisons in clinical pharmacology studies
and other areas.
