Bismuth Subsalicylate Oral Suspension

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 Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of bismuth subsalicylate (C₇H₅BiO₄). It may contain one or more suitable buffers, coloring agents, flavors, preservatives, stabilizers, sweeteners, and suspending agents.

2 IDENTIFICATION

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

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

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 solution: Transfer 10 g of Oral Suspension, previously well shaken in its original container to ensure homogeneity, to a 200-mL volumetric flask. Add about 100 mL of 1 N nitric acid, and dilute with 1 N nitric acid to volume. Mix well without shaking, transfer 10.0 mL of this mixture to a 100-mL volumetric flask, and dilute with 1 N nitric acid to volume. Centrifuge about 20 mL 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: 1 N nitric acid

Analysis

Samples: Standard solution, Sample solution, and Blank

Transfer a measured volume of the Sample solution that contains 0.9 mg of bismuth subsalicylate and 10 mL of the Standard solution to separate 50-mL volumetric flasks. Add 10.0 mL of 10% ascorbic acid solution and 25.0 mL of 20% potassium iodide solution to each volumetric flask, and dilute with water to volume. Concomitantly determine the absorbances of both solutions, using the Blank to set the spectrophotometer.

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

Result = (A_U/A_S) x (C_S/C_U) x (M_r1/M_r2) x 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 bismuth subsalicylate in 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 SPECIFIC TESTS

MICROBIAL ENUMERATION TESTS (61) and TESTS FOR SPECIFIED MICROORGANISMS (62): The total aerobic microbial count is NMT 10² cfu/g, and the total combined molds and yeasts count is NMT 5 x 10¹ cfu / g It meets the requirements of the test for the absence of Escherichia coli.

PH (791): 3.0-5.5

5 ADDITIONAL REQUIREMENTS

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