21 CFR § 331.21 - Test modifications.

---
identifier: "/us/cfr/t21/s331.21"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 331.21 - Test modifications."
title_number: 21
title_name: "Food and Drugs"
section_number: "331.21"
section_name: "Test modifications."
chapter_name: "FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "D"
subchapter_name: "DRUGS FOR HUMAN USE"
part_number: "331"
part_name: "ANTACID PRODUCTS FOR OVER-THE-COUNTER (OTC) HUMAN USE"
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, 353, 355, 360, 371."
regulatory_source: "39 FR 19874, June 4, 1974, unless otherwise noted."
cfr_part: "331"
---


# 331.21 Test modifications.

The formulation or mode of administration of certain products may require a modification of the United States Pharmacopeia 23/National Formulary 18 acid neutralizing capacity test. Any proposed modification and the data to support it shall be submitted as a petition under the rules established in § 10.30 of this chapter. All information submitted will be subject to the disclosure rules in part 20 of this chapter.

[61 FR 4823, Feb. 8, 1996]