Calcium Carbonate and Magnesia Tablets
DEFINITION
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].
IDENTIFICATION
• A. Identification Tests—General, 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.
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 Tests—General, Magnesium 191
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.
ASSAY
• 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. [Note—Reserve 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 ammonia–ammonium 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%
PERFORMANCE TESTS
• Uniformity of Dosage Units 905:
Meet the requirements for Weight Variation with respect to calcium carbonate and to magnesia
905:
Meet the requirements for Weight Variation with respect to calcium carbonate and to magnesia
SPECIFIC TESTS
• Acid-Neutralizing Capacity 301
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)]
| FM | = | = theoretical acid-neutralizing capacity of Mg(OH)2, 0.0343 mEq |
| M | = | = quantity of Mg(OH)2 in the sample tested (mg), based on the labeled quantity |
| FC | = | = theoretical acid-neutralizing capacity of CaCO3, 0.02 mEq |
| C | = | = quantity of CaCO3 in the sample tested (mg), based on the labeled quantity |
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Elena Gonikberg, Ph.D.
Principal Scientific Liaison 1-301-816-8251 |
(SM32010) Monographs - Small Molecules 3 |
USP35–NF30 Page 2446
Pharmacopeial Forum: Volume No. 33(2) Page 211