21 CFR § 320.28 - Correlation of bioavailability with an acute pharmacological effect or clinical evidence.
---
identifier: "/us/cfr/t21/s320.28"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 320.28 - Correlation of bioavailability with an acute pharmacological effect or clinical evidence."
title_number: 21
title_name: "Food and Drugs"
section_number: "320.28"
section_name: "Correlation of bioavailability with an acute pharmacological effect or clinical evidence."
chapter_name: "FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "D"
subchapter_name: "DRUGS FOR HUMAN USE"
part_number: "320"
part_name: "BIOAVAILABILITY AND BIOEQUIVALENCE REQUIREMENTS"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "21 U.S.C. 321, 351, 352, 355, 371."
cfr_part: "320"
---
# 320.28 Correlation of bioavailability with an acute pharmacological effect or clinical evidence.
Correlation of in vivo bioavailability data with an acute pharmacological effect or clinical evidence of safety and effectiveness may be required if needed to establish the clinical significance of a special claim, e.g., in the case of an extended release preparation.
[42 FR 1648, Jan. 7, 1977, as amended at 67 FR 77674, Dec. 19, 2002]