Clinical DevelopmentLast reviewed April 2026

Bioequivalence(BE)

The absence of a significant difference in the rate and extent to which the active ingredient in two pharmaceutically equivalent products becomes available at the site of drug action.

Usage Examples

The BE study showed the generic was bioequivalent to the RLD with 90% CI within 95-108%.
A BCS Class I biowaiver eliminated the need for a clinical BE study.
The narrow therapeutic index drug required tighter BE criteria of 90-111%.

What is BE?

Bioequivalence (BE) is the regulatory standard generic drug (ANDA) and many 505(b)(2) applicants must meet to demonstrate their product performs equivalently to the Reference Listed Drug. BE is typically established through pharmacokinetic studies comparing the test product and reference product in healthy volunteers, measuring Cmax (peak plasma concentration), AUC (total exposure), and Tmax (time to peak) after administration.

Under FDA rules, the test product is considered bioequivalent if the 90% confidence intervals for the geometric mean ratios of Cmax and AUC between test and reference fall within 80-125% of each other. This range reflects the biological variability acceptable for clinically interchangeable products. Certain narrow therapeutic index drugs require tighter BE criteria.

Some drug products can obtain a biowaiver in lieu of clinical BE studies — most commonly through the Biopharmaceutics Classification System (BCS) for highly soluble, highly permeable drugs in immediate-release solid oral dosage forms. For biologics, the BE concept is replaced by biosimilarity, which requires a broader evidence package because biological product sameness cannot be demonstrated by PK alone.

Regulatory Context

This term appears most often in clinical development workflows where submission quality, regulatory evidence, and audit readiness depend on consistent language. It is commonly referenced alongside 21 CFR 320, FDCA SECTION 505J.

FDAEMAPMDA

When This Matters

The BE study showed the generic was bioequivalent to the RLD with 90% CI within 95-108%.
A BCS Class I biowaiver eliminated the need for a clinical BE study.
The narrow therapeutic index drug required tighter BE criteria of 90-111%.

Common Mistakes

Applying one-region clinical assumptions to global submission strategies.
Missing protocol-to-regulation traceability for pivotal studies.
Underestimating how regional guidance updates impact trial documentation.

Related Regulations

21 CFR 320FDCA SECTION 505J

Frequently Asked Questions

For most drugs, the 90% confidence interval for the geometric mean ratio (test vs. reference) of Cmax and AUC must fall within 80-125%. Narrow therapeutic index drugs have tighter limits (typically 90-111% for Cmax and AUC) under FDA's current guidance.

Under the Biopharmaceutics Classification System, certain immediate-release solid oral dosage forms can be exempt from clinical BE studies if the drug substance is highly soluble and highly permeable (BCS Class I), and the drug product shows rapid in vitro dissolution. BCS Class III waivers are also available under more restrictive conditions.

Bioequivalence applies to small-molecule drugs where sameness can be demonstrated through PK equivalence. Biosimilarity applies to biologics where biological complexity precludes demonstrating sameness; biosimilars require extensive analytical characterization, nonclinical studies, and comparative clinical efficacy and safety data instead.