part_subject: "ANTACID PRODUCTS FOR OVER-THE-COUNTER (OTC) HUMAN USE"
subpart_code: "C"
subpart_subject: "Testing Procedures"
section_number: "331.20"
section_subject: "Determination of percent contribution of active ingredients."
cfr_reference: "21 CFR 331.20"
title_name: "Title 21"
title_subject: "Food and Drugs"
parts_covered: "Parts 300 to 499"
revised_date: "Revised as of April 1, 2019"
publication_date: "As of April 1, 2019"
contains_description: "Containing a codification of documents of general applicability and future effect"
publication_info: "Published by the Office of the Federal Register National Archives and Records Administration as a Special Edition of the Federal Register"
---
To determine the percent contribution of an antacid active ingredient, place an accurately weighed amount of the antacid active ingredient equal to the amount present in a unit dose of the product into a 250-milliliter (mL) beaker. If wetting is desired, add not more than 5 mL of alcohol (neutralized to an apparent pH of 3.5), and mix to wet the sample thoroughly. Add 70 mL of water, and mix on a magnetic stirrer at 300 ±30 r.p.m. for 1 minute. Analyze the acid neutralizing capacity of the sample according to the procedure provided in the United States Pharmacopeia 23/National Formulary 18 and calculate the percent contribution of the antacid active ingredient in the total product as follows: