21 CFR § 331.10 - Antacid active ingredients.

---
identifier: "/us/cfr/t21/s331.10"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 331.10 - Antacid active ingredients."
title_number: 21
title_name: "Food and Drugs"
section_number: "331.10"
section_name: "Antacid active ingredients."
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"
---


# 331.10 Antacid active ingredients.

(a) The active antacid ingredients of the product consist of one or more of the ingredients permitted in § 331.11 within any maximum daily dosage limit established, each ingredient is included at a level that contributes at least 25 percent of the total acid neutralizing capacity of the product, and the finished product contains at least 5 meq of acid neutralizing capacity as measured by the procedure provided in the United States Pharmacopeia 23/National Formulary 18. The method established in § 331.20 shall be used to determine the percent contribution of each antacid active ingredient.

(b) This section does not apply to an antacid ingredient specifically added as a corrective to prevent a laxative or constipating effect.

[39 FR 19874, June 4, 1974, as amended at 61 FR 4822, Feb. 8, 1996]