Calcium Carbonate Lozenges

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 Carbonate Lozenges contain NLT 90.0% and NMT 110.0% of the labeled amount of calcium carbonate (CaCO₃) 

2 IDENTIFICATION 

A. Identification Tests—General, Calcium〈191〉: The addition of 6 N hydrochloric acid to a Lozenge produces effervescence, and the resulting solution, after being boiled to expel carbon dioxide and then neutralized with 6 N ammonium hydroxide, meets the requirements of the tests. 

3 ASSAY 

Procedure 

[Note—The Standard solutions and the Sample solution may be modified, if necessary, to obtain solutions of suitable concentrations adaptable to the linear or working range of the instrument.] 

Lanthanum chloride solution: Transfer 10 g of potassium chloride and 20 g of lanthanum chloride to a 2000-mL volumetric flask. Add 1000 mL of water and 40 mL of hydrochloric acid, mix, and allow to cool. Dilute with water to volume. 

Standard stock solution: Transfer 250 mg of chelometric standard calcium carbonate, previously dried at 110° for 2 h and then cooled in a 

desiccator, to a 500-mL volumetric flask. Add 100 mL of water and 12 mL of 1 N hydrochloric acid, swirl to dissolve the calcium carbonate, and allow to cool. Dilute with water to volume. This stock solution contains about 500 µg/mL of calcium carbonate. Standard solutions: To three separate 100-mL volumetric flasks add 2.0, 3.0, and 4.0 mL of the Standard stock solution, and dilute each with Lanthanum chloride solution to volume. These Standard solutions contain 10, 15, and 20 µg/mL of calcium carbonate, respectively. Sample stock solution: Transfer the equivalent to 3000 mg of calcium carbonate, from powdered Lozenges, to a 1000-mL volumetric flask. Add 100 mL of 1 N hydrochloric acid and 300 mL of water, and sonicate to dissolve the powder. Dilute with water to volume. Sample solution: Transfer 5.0 mL of Sample stock solution to a 1000-mL volumetric flask, and dilute with Lanthanum chloride solution to volume. 

Instrumental conditions 

(See Atomic Absorption Spectroscopy 〈852〉.) 

Mode: Atomic absorption spectrophotometry 

Lamp: Calcium hollow-cathode 

Flame: Nitrous oxide–acetylene 

Analytical wavelength: Calcium emission line at 422.7 nm 

Blank: Lanthanum chloride solution 

Analysis 

Samples: Standard solutions, Sample solution, and Blank 

Plot the absorbances of the Standard solutions versus their concentrations of calcium carbonate, in µg/mL, by drawing a straight line best tting the three plotted points. From the graph determine the concentration, C, in µg/mL, of calcium carbonate in the Sample solution. Calculate the percentage of label claim of calcium carbonate (CaCO₃) in the portion of Lozenges taken: 

Result = (C/C_U) × 100 

C = measured concentration of calcium carbonate in the Sample solution (µg/mL), as calculated above 

C_U = nominal concentration of calcium carbonate in the Sample solution (µg/mL) 

Acceptance criteria: 90.0%–110.0% 

4 OTHER COMPONENTS 

Sodium Content (if so labeled) 

[Note—The Standard solutions and the Sample solution may be modified, if necessary, to obtain solutions of suitable concentrations adaptable to the linear or working range of the instrument.] 

Standard stock solution: Transfer 2.542 g of sodium chloride, previously dried at 105° for 2 h, to a 1000-mL volumetric flask. Dissolve in and dilute with water to volume. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, and dilute with water to volume. Standard solutions: To three separate 100-mL volumetric flasks, add 1.0, 3.0, and 5.0 mL of the Standard stock solution, and dilute each with water to volume. These Standard solutions contain 1.0, 3.0, and 5.0 µg/mL of sodium, respectively. 

Sample stock solution: Prepare as directed in the Assay. Pass a portion of it, if necessary, through a filter of 0.5-µm or finer pore size, and use the clear solution. 

Sample solution: Transfer 10.0 mL of the Sample stock solution to a 25-mL volumetric flask, and dilute with water to volume. Instrumental conditions 

(See Atomic Absorption Spectroscopy 〈852〉.) 

Mode: Atomic absorption spectrophotometry 

Lamp: Sodium hollow-cathode 

Flame: Air–acetylene 

Analytical wavelength: Sodium emission line at 589.6 nm 

Blank: Water 

Analysis 

Samples: Standard solutions, Sample solution, and Blank 

Plot the absorbances of the Standard solutions versus their contents of sodium, in µg/mL, by drawing a straight line best fitting the three plotted points. From the graph determine the quantity, C, in µg, of sodium in each mL of the Sample solution. 

Calculate the percentage of label claim of sodium in the portion of Lozenges taken: 

Result = (C/C_U ) × 100  

C = measured concentration of sodium in the Sample solution (µg/mL), as calculated above 

C_U = nominal concentration of sodium in the Sample solution (µg/mL) 

Acceptance criteria: NMT 115.0% of the labeled amount 

5 PERFORMANCE TESTS 

Uniformity of Dosage Units 〈905〉: Meet the requirements 

6 SPECIFIC TESTS 

Acid-Neutralizing Capacity 〈301〉  

Analysis: The acid consumed by the minimum single dose recommended in the labeling is NLT 5 mEq of acid and NLT the number of mEq calculated by: 

Result = (F_C × C) × 0.9 

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

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

7 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in well-closed containers.