Calcium and Magnesium Carbonates Tablets

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

DOWNLOAD PDF HERE

1 DEFINITION

Calcium and Magnesium Carbonates Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of calcium carbonate (CaCO₃) and NLT 85.0% and NMT 115.0% of the labeled amount of magnesium carbonate (MgCO₃).

2 IDENTIFICATION

A. Identification Tests—General, Calcium〈191〉: The addition of 1 N hydrochloric acid to 1 Tablet produces effervescence, and the resulting solution, after having been filtered, meets the requirements of the tests.

B. Identification Tests—General, 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: Meets the requirements

3 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 the aid of 25 mL of water, and add 10 mL of 1 N hydrochloric acid. Heat on a steam bath for 30 min, allow to cool, and transfer to a 100-mL volumetric flask with the aid of water. Dilute with water to volume, mix, filter, and use the filtrate. [Note—Reserve a portion of the
ltrate for the Sample solution in the Magnesium Carbonate test.]

Analysis: Transfer 20.0 mL of Sample solution to a suitable container. Dilute with water to 100 mL, and add 15 mL of 1 N sodium hydroxide, 5mL of triethanolamine, and 100 mg of hydroxy naphthol blue. Titrate with 0.05 M edetate disodium VS until the solution is deep blue. Each mL of 0.05 M edetate disodium is equivalent to 5.004 mg of CaCO₃ .

Acceptance criteria: 90.0%–110.0%

Magnesium Carbonate

Sample solution: Use a portion of the filtrate from the Sample solution in the Calcium Carbonate test.

Analysis: Transfer the Sample solution, equivalent to 120 mg of calcium carbonate and magnesium carbonate 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. From the volume of 0.05 M edetate disodium consumed, subtract the volume of 0.05 M edetate disodium corresponding to the content of calcium carbonate in the portion of the Sample solution taken. The difference is the volume of 0.05 M edetate disodium equivalent to the quantity of magnesium carbonate present. Each mL of 0.05 M edetate disodium is equivalent to 4.216 mg of MgCO₃

Acceptance criteria: 85.0%–115.0%

4 PERFORMANCE TESTS

Disintegration 〈701〉

Time: NMT 10 min, except that where Tablets are labeled as gelatin-coated, the time is NMT 30 min, simulated gastric fluid TS being substituted for water in the test

Uniformity of Dosage Units 〈905〉: Meet the requirements for Weight Variation with respect to calcium carbonate and to magnesium carbonate

5 SPECIFIC TESTS

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:

Result = [(F_M × M) × 0.8] + [(F_C × C) × 0.9]

F_M = theoretical acid-neutralizing capacity of MgCO₃ , 0.024 mEq

M = quantity of MgCO₃ in the specimen tested, based on the labeled quantity (mg)

F_C = theoretical acid-neutralizing capacity of CaCO₃ , 0.02 mEq

C = quantity of CaCO₃ in the specimen tested, based on the labeled quantity (mg)

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

Labeling: Tablets that are gelatin-coated are so labeled.