Calcium Carbonate and Magnesia Tablets
»Calcium Carbonate and Magnesia Tablets contain not less than 90.0percent and not more than 110.0percent of the labeled amount of calcium carbonate (CaCO3)and not less than 90.0percent and not more than 115.0percent of the labeled amount of magnesium hydroxide [Mg(OH)2].
Packaging and storage— Preserve in well-closed containers.
Labeling— Label the Tablets to indicate that they are to be chewed before being swallowed.
Identification—
A: The addition of 3Nhydrochloric acid to the Tablets produces effervescence,and the resulting solution,after being boiled to expel carbon dioxide and neutralized with 6Nammonium hydroxide,meets the requirements of the tests for Calcium á191ñ.
B: Heat 2Tablets in 20mLof 1Nsulfuric acid.Cool,add 20mLof alcohol,mix,and allow to stand for 30minutes.Filter this solution,and add 2mLof 1Nhydrochloric acid to the filtrate:this solution meets the requirements of the tests for Magnesium á191ñ.
Uniformity of dosage units á905ñ: meet the requirements for Weight Variationwith respect to calcium carbonate and to magnesia.
Acid-neutralizing capacity á301ñ— Not less than 5mEq 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:
0.8(0.0343M)+0.9(0.02C),
in which 0.0343and 0.02are the theoretical acid-neutralizing capacities,in mEq,of Mg(OH)2and CaCO3,respectively;and Mand Care the respective quantities,in mg,of Mg(OH)2and CaCO3in the specimen tested,based on the labeled quantities.
Assay for calcium carbonate— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 400mg of calcium carbonate,to a beaker with 25mLof water,and add 40mLof 1Nhydrochloric acid.Heat on a steam bath for 30minutes,allow to cool,transfer to a 100-mLvolumetric flask with the aid of water,dilute with water to volume,mix,and filter.Transfer 20.0mLof the filtrate to a suitable container,dilute with water to 100mL,add 30mLof 1Nsodium hydroxide,5mLof triethanolamine,and 100mg of hydroxy naphthol blue,and titrate with 0.05Medetate disodium VSuntil the solution is deep blue in color.Each mLof 0.05Medetate disodium is equivalent to 5.004mg 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 120mg of calcium carbonate and magnesium hydroxide combined,to a suitable container,dilute with water to 100mL,add 10mLof ammonia–ammonium chloride buffer TS,5mLof triethanolamine,and 0.3mLof eriochrome black TS,and titrate with 0.05Medetate disodium VSto a blue endpoint.The volume,in mL,of 0.05Medetate disodium consumed,less the volume of 0.05Medetate disodium corresponding to the content of calcium carbonate in the volume,in mL,of the filtrate taken,represents the volume,in mL,of 0.05Medetate disodium equivalent to the quantity of magnesium hydroxide present.Each mLof 0.05Medetate disodium is equivalent to 2.916mg of Mg(OH)2.
Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(PA4)Pharmaceutical Analysis 4
USP28–NF23Page 321
Pharmacopeial Forum:Volume No.29(6)Page 1852
Phone Number:1-301-816-8251