{"data":{"id":"us/21-cfr-331.20","jurisdiction":"us","citation":"21 CFR 331.20","heading":"Determination of percent contribution of active ingredients.","body":"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:\nPercent contribution = (Total mEq. Antacid Active Ingredient × 100)/(Total mEq. Antacid Product).","path":["Title 21—Food and Drugs","CHAPTER I—FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES","SUBCHAPTER D—DRUGS FOR HUMAN USE","PART 331—ANTACID PRODUCTS FOR OVER-THE-COUNTER (OTC) HUMAN USE","Subpart C—Testing Procedures"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-21.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:24:47Z","sha256":"18c6b325a152888e8ec3039968230acaec7fb077f3d3841c6055be76b06a6475","source_id":"us-cfr","stale":true,"prev":"us/21-cfr-331.15","next":"us/21-cfr-331.21"},"notice":"GroundRules: Original legal text. Not legal advice."}