Packaging and storage— Preserve in well-closed containers.

Labeling— After February 1, 2011, Calcium Carbonate and Magnesia Tablets that must be chewed must be titled Calcium Carbonate and Magnesia Chewable Tablets provided they comply with the requirements of that monograph. Until that time, the title Calcium Carbonate and Magnesia Tablets can be used for Tablets that can be administered without chewing and for Tablets that must be chewed. In the latter case, the Tablets are to be labeled to indicate that they are to be chewed before being swallowed.

Identification—

Uniformity of dosage units 905: meet the requirements for Weight Variation with respect to calcium carbonate and to magnesia.

Acid-neutralizing capacity 301— Not less than 5 mEq of acid is consumed by the minimum single dose recommended in the labeling, and not less than the number of mEq calculated by the formula: in which 0.0343 and 0.02 are the theoretical acid-neutralizing capacities, in mEq, of Mg(OH)2 and CaCO3, respectively; and M and C are the respective quantities, in mg, of Mg(OH)2 and CaCO3 in the specimen tested, based on the labeled quantities.

Assay for calcium carbonate— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 400 mg of calcium carbonate, to a beaker with 25 mL of water, and add 40 mL of 1 N hydrochloric acid. Heat on a steam bath for 30 minutes, allow to cool, transfer to a 100-mL volumetric flask with the aid of water, dilute with water to volume, mix, and filter. Transfer 20.0 mL of the filtrate to a suitable container, dilute with water to 100 mL, add 30 mL of 1 N sodium hydroxide, 5 mL of triethanolamine, and 100 mg of hydroxy naphthol blue, and 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 calcium carbonate (CaCO3).

Assay for magnesium hydroxide— Transfer an accurately measured portion of the filtrate remaining from the Assay for calcium carbonate, equivalent to about 120 mg of calcium carbonate and magnesium hydroxide combined, to a suitable container, dilute with water to 100 mL, add 10 mL of ammonia–ammonium chloride buffer TS, 5 mL of triethanolamine, and 0.3 mL of eriochrome black TS, and 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 filtrate 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.

Topic/Question	Contact	Expert Committee
Monograph	Elena Gonikberg, Ph.D. Senior Scientist 1-301-816-8345	(MDGRE05) Monograph Development-Gastrointestinal Renal and Endocrine

USP32–NF27 Page 1756