Calcium Carbonate and Magnesia Chewable Tablets
(Title for this new monographto become official February 1, 2011)
(Prior to February 1, 2011, the current practice of labeling the article of commerce with the name Calcium Carbonate and Magnesia Tablets may be continued)
» Calcium Carbonate and Magnesia Chewable Tablets contain not less than 90.0 percent and not more than 110.0 percent of the labeled amount of calcium carbonate (CaCO3) and not less than 90.0 percent and not more than 115.0 percent of the labeled amount of magnesium hydroxide [Mg(OH)2].
Packaging and storage Preserve in well-closed containers.
Labeling Label the Chewable Tablets to indicate that they must be chewed before being swallowed.
A: The addition of 3 N hydrochloric acid to the Chewable Tablets produces effervescence, and the resulting solution, after being boiled to expel carbon dioxide and neutralized with 6 N ammonium hydroxide, meets the requirements of the tests for Calcium 191.
B: Heat 2 Chewable Tablets in 20 mL of 1 N sulfuric acid. Cool, add 20 mL of alcohol, mix, and allow to stand for 30 minutes. Filter this solution, and add 2 mL of 1 N hydrochloric acid to the filtrate: this solution meets the requirements of the tests for Magnesium 191.
Uniformity of dosage units 905: meet the requirements for Weight Variation with respect to calcium carbonate and to magnesia.
Acid-neutralizing capacity 301 The acid consumed by the minimum single dose recommended in the labeling is not less than 5 mEq and not less than the number of mEq calculated by the formula:
0.8(0.0343M ) + 0.9(0.02C)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 Chewable 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 ammoniaammonium 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.
(Official February 1, 2011)
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USP32NF27 Page 1757Pharmacopeial Forum: Volume No. 33(2) Page 212