Bismuth Subsalicylate Tablets

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

Bismuth Subsalicylate Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of bismuth subsalicylate (C₇H₅BiO₄).

2 IDENTIFICATION

A. IDENTIFICATION TESTS-GENERAL, Bismuth (191): Meet the requirements

B. IDENTIFICATION TESTS-GENERAL (191), Salicylate: After acidifying with nitric acid, it meets the requirements of test A.

3 ASSAY

3.1 PROCEDURE

Standard stock solution: 2.5 mg/mL of bismuth in nitric acid. Prepare by dissolving in 6% of the flask volume of nitric acid, and diluting with 0.01 N nitric acid to volume.

Standard solution: 0.05 mg/mL of bismuth in 1 N nitric acid from the Standard stock solution

Sample stock solution: Equivalent to 90 mg of bismuth subsalicylate from finely powdered Tablets in a 200-mL volumetric flask. Add 150 mL of 1 N nitric acid, and sonicate for 2 min. Dilute with 1 N nitric acid to volume.

Sample solution: Transfer 20.0 mL of the Sample stock solution to a 100-mL volumetric flask, and dilute with 1 N nitric acid to volume.

Centrifuge a portion at 4500 rpm for at least 10 min.

Instrumental conditions

(See Ultraviolet-Visible Spectroscopy (857).)

Mode: UV-Vis

Analytical wavelength: 463 nm

Cell: 1 cm

Blank: 10% ascorbic acid solution, 20% potassium iodide solution, and 1 N nitric acid (2:5:1)

Analysis

Samples: Standard solution and Sample solution

Transfer 10.0 mL of the Standard solution and the Sample solution to separate 50.0-mL volumetric flasks, and dilute with the Blank to volume. Concomitantly determine the absorbance of the solutions at the wavelength of maximum absorbance at 463 nm with a suitable spectrophotometer, using the combined reagent solutions as the blank.

Calculate the percentage of the labeled amount of bismuth subsalicylate (C₇H₅BiO₄) in the portion of Tablets taken:

Result = (A_U/A_S) × (C_S/C_U) x (M_r1/M_r2) × 100

A_U = absorbance of the Sample solution

A_S = absorbance of the Standard solution

C_S = concentration of bismuth in the Standard solution (mg/mL)

C_U = nominal concentration of the Sample solution (mg/mL)

M_r1 = molecular weight of bismuth subsalicylate, 362.09

M_r2 = molecular weight of bismuth, 208.98

Acceptance criteria: 90.0%-110.0%

4 PERFORMANCE TESTS

DISINTEGRATION (701)

This test does not apply to Tablets labeled as chewable.

Time: 10 min

Acceptance criteria: Meet the requirements

5 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers. Avoid excessive heat (over 40°).

LABELING: Label chewable Tablets to indicate that they are to be chewed before swallowing.