Methenamine Mandelate 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 Mandelate Tablets contain NLT 95.0% and NMT 105.0% of the labeled amount of methenamine mandelate (C₆H₁₂N₄ · C₈H₈O₃).

2 IDENTIFICATION

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

Sample: Triturate a portion of finely powdered Tablets, equivalent to 5.0 mg of methenamine mandelate, with 5 mL of chloroform, and pass through a 0.45-μm membrane filter. Evaporate the solvent, and allow the residue to air-dry.

Acceptance criteria: Meet the requirements

3 ASSAY

Procedure

Sample solution: Transfer an equivalent to 60 mg of methenamine mandelate, from NLT 20 finely powdered Tablets, to a 250-mL conical flask. Add 15 mL of dehydrated alcohol, stir to dissolve, and add 40 mL of chloroform.

Titrimetric system

Mode: Direct titration

Titrant: 0.05 N silver nitrate in dehydrated alcohol prepared as follows. Dissolve by stirring 8.5 g of silver nitrate in 1000 mL of dehydrated alcohol. Transfer 100 mg of sodium chloride, previously dried at 110° for 2 h, to a 100-mL beaker, and dissolve in 50 mL of water. Titrate with the silver nitrate solution to the potentiometric endpoint, using a silver billet indicator electrode and a silver–silver chloride double-junction reference electrode containing a potassium nitrate salt bridge. Calculate the normality of the titrant.

Endpoint detection: Potentiometric

Analysis: Titrate the Sample solution with Titrant, determining the endpoint potentiometrically, using a silver billet indicator electrode and a silver–silver chloride double-junction reference electrode containing a potassium nitrate salt bridge. Each mL of 0.05 N silver nitrate is equivalent to 7.308 mg of methenamine mandelate (C₆H₁₂N₄ · C₈H₈O₃).

Acceptance criteria: 95.0%–105.0%

4 PERFORMANCE TESTS

Dissolution 〈711〉

For uncoated or plain coated Tablets

Medium: Water; 900 mL

Apparatus 1: 100 rpm

Time: 45 min

Standard solution: USP Methenamine Mandelate RS in Medium

Instrumental conditions

Mode: UV

Analytical wavelength: UV maximum at about 257 nm

Analysis: Determine the amount of methenamine mandelate (C₆H₁₂N₄ · C₈H₈O₃) dissolved in the portion of the solution under test, passed through a filter of 0.45-μm pore size and suitably diluted with Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Methenamine Mandelate RS in the same Medium.

Tolerances: NLT 75% (Q) of the labeled amount of methenamine mandelate (C₆H₁₂N₄ · C₈H₈O₃) is dissolved.

Uniformity of Dosage Units 〈905〉: Meet the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

USP Reference Standards 〈11〉

USP Methenamine Mandelate RS