Methenamine Hippurate 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

Methenamine Hippurate Tablets contain NLT 95.0% and NMT 105.0% of the labeled amount of methenamine hippurate (C₆H₁₂N₄ · C₉H₉NO₃).

2 IDENTIFICATION

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A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197M (CN 1-May-2020)

Sample: A portion of finely powdered Tablets

Acceptance criteria: Meet the requirements

3 ASSAY

Procedure

Sample solution: Transfer an equivalent to 700 mg of methenamine hippurate from finely powdered Tablets (NLT 20) to a 250-mL conical flask. Add 50 mL of alcohol, then add thymolphthalein TS.

Titrimetric system

Mode: Direct titration

Titrant: 0.1 N sodium hydroxide VS

Endpoint detection: Visual

Analysis: Titrate the Sample solution with Titrant. Perform a blank determination on a mixture of 50 mL of alcohol and 20 mL of water, and

make any necessary correction. Each mL of 0.1 N sodium hydroxide is equivalent to 31.94 mg of methenamine hippurate (C₆H₁₂N₄ · C₉H₉NO₃).

Acceptance criteria: 95.0%–105.0%

4 PERFORMANCE TESTS

Dissolution 〈711〉

Test 1

Medium: Water; 900 mL

Apparatus 2: 100 rpm

Time: 30 min

Standard solution: 22 μg/mL of USP Methenamine Hippurate RS

Instrumental conditions

Mode: UV

Analytical wavelength: Maxima at about 227 nm

Analysis: Determine the quantity of methenamine hippurate (C₆H₁₂N₄ · C₉H₉NO₃) dissolved of filtered portions of the solution under test, suitably diluted with water if necessary, in comparison with the Standard solution.

Tolerances: NLT 80% (Q) of the labeled amount of methenamine hippurate (C₆H₁₂N₄ · C₉H₉NO₃) is dissolved.

Test 2

[Note—If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 2.]

Medium: Water; 900 mL

Apparatus 2: 50 rpm

Time: 60 min

Standard solution: 22 μg/mL of USP Methenamine Hippurate RS

Instrumental conditions

Mode: UV

Analytical wavelength: Maxima at about 227 nm

Analysis: Determine the quantity of methenamine hippurate (C₆H₁₂N₄ · C₉H₉NO₃) dissolved of filtered portions of the solution under test, suitably diluted with water if necessary, in comparison with the Standard solution.

Tolerances: NLT 80% (Q) of the labeled amount of methenamine hippurate (C₆H₁₂N₄ · C₉H₉NO₃) is dissolved.

Uniformity of Dosage Units 〈905〉: Meet the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

Labeling: When more than one Dissolution test is given, the labeling states the Dissolution test used only if Test 1 is not used.

USP Reference Standards 〈11〉

USP Methenamine Hippurate RS