Calcium and Magnesium Carbonates Oral Suspension

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

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

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1 DEFINITION

Calcium and Magnesium Carbonates Oral Suspension contains 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 3 N hydrochloric acid to a quantity of Oral Suspension, equivalent to 500 mg of calcium carbonate, produces effervescence, and the resulting solution, after having been filtered, meets the requirements.

B. Identification Tests—General, Magnesium 〈191〉

Sample solution: Heat a quantity of Oral Suspension, equivalent to 800 mg of magnesium carbonate, with 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: Transfer a portion of Oral Suspension equivalent to 400 mg of calcium carbonate, previously well shaken in its original container and free of air bubbles, to a beaker, with the aid of 20 mL of water, and add 10 mL of 1 N hydrochloric acid. Heat on a steam bath for 30 min, allow to cool, transfer with the aid of water to a 100-mL volumetric flask, dilute with water to volume, filter and use the filtrate. [Note—Reserve a portion of the filtrate 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

Deliverable Volume 〈698〉: Meets the requirements

5 SPECIFIC TESTS

Microbial Enumeration Tests 〈61〉andTests for Specified Microorganisms 〈62〉: The total aerobic microbial count is NMT 100 cfu/mL, and it meets the requirements of the tests for absence of Escherichia coli and Pseudomonas aeruginosa.

pH 〈791〉: 7.0–8.6

Acid-Neutralizing Capacity 〈301〉: 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 tight containers, and avoid freezing.