Calcium Carbonate and Magnesia Tablets
Calcium Carbonate and Magnesia Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of calcium carbonate (CaCO3) and NLT 90.0% and NMT 115.0% of the labeled amount of magnesium hydroxide [Mg(OH)2].
• A. Identification TestsGeneral, Calcium 191: The addition of 3 N hydrochloric acid to the Tablets produces effervescence. The resulting solution, after being boiled to expel carbon dioxide and neutralized with 6 N ammonium hydroxide, meets the requirements of the tests.
• B. Identification TestsGeneral, Magnesium 191
Sample solution: Heat 2 Tablets in 20 mL of 1 N sulfuric acid. Cool, add 20 mL of alcohol, mix, and allow to stand for 30 min. Filter this solution, and add 2 mL of 1 N hydrochloric acid to the filtrate.
Acceptance criteria: The solution meets the requirements.
• Calcium Carbonate
Sample solution: Finely powder NLT 20 Tablets. Transfer a portion of the powder, equivalent to 400 mg of calcium carbonate, to a beaker with 25 mL of water. Add 40 mL of 1 N hydrochloric acid. Heat on a steam bath for 30 min, allow to cool, and transfer with the aid of water to a 100-mL volumetric flask. Dilute with water to volume, mix, filter, and use the filtrate. [NoteReserve a portion of it for the test for Magnesium Hydroxide. ]
Analysis: Transfer 20.0 mL of the Sample solution to a suitable container, dilute with water to 100 mL, and add 30 mL of 1 N sodium hydroxide, 5 mL of triethanolamine, and 100 mg of hydroxy naphthol blue. Titrate with 0.05 M edetate disodium VS until the solution is deep blue in color. Each mL of 0.05 M edetate disodium is equivalent to 5.004 mg of CaCO3.
Acceptance criteria: 90.0%110.0%
• Magnesium Hydroxide
Sample solution: Use the Sample solution from the test for Calcium Carbonate.
Analysis: Transfer a portion of the Sample solution, equivalent to 120 mg of calcium carbonate and magnesium hydroxide combined, to a suitable container. Dilute with water to 100 mL, and add 10 mL of ammoniaammonium chloride buffer TS, 5 mL of triethanolamine, and 0.3 mL of eriochrome black TS. Titrate with 0.05 M edetate disodium VS to a blue endpoint. The volume, in mL, of 0.05 M edetate disodium consumed, less the volume of 0.05 M edetate disodium corresponding to the content of calcium carbonate in the volume, in mL, of the Sample solution taken, represents the volume, in mL, of 0.05 M edetate disodium equivalent to the quantity of magnesium hydroxide present. Each mL of 0.05 M edetate disodium is equivalent to 2.916 mg of Mg(OH)2.
Acceptance criteria: 90.0%115.0%
• Uniformity of Dosage Units 905: Meet the requirements for Weight Variation with respect to calcium carbonate and to magnesia
• Acid-Neutralizing Capacity 301
Analysis: NLT 5 mEq of acid is consumed by the minimum single dose recommended in the labeling, and NLT the number of mEq calculated by the formula:
Result = [0.8 × (FM × M)] + [0.9 × (FC × C)]
• Packaging and Storage: Preserve in well-closed containers.
Auxiliary Information Please check for your question in the FAQs before contacting USP.
USP35NF30 Page 2446Pharmacopeial Forum: Volume No. 33(2) Page 211