U.S. PHARMACOPEIA

Search USP29  
Methenamine Hippurate Tablets
» Methenamine Hippurate Tablets contain not less than 95.0 percent and not more than 105.0 percent of the labeled amount of methenamine hippurate (C6H12N4·C9H9NO3).
Packaging and storage— Preserve in well-closed containers.
Add the following:
Labeling— When more than one Dissolution test is given, the labeling states the Dissolution test used only if Test 1 is not used.USP29
Identification— A portion of finely powdered Tablets responds to the Identification test under Methenamine Hippurate.
Change to read:
Dissolution 711—
Test 1—USP29
Medium: water; 900 mL.
Apparatus 2: 100 rpm.
Time: 30 minutes.
Standard solution— Dissolve an accurately weighed quantity of USP Methenamine Hippurate RS in water to obtain a solution having a known concentration of about 22 µg per mL.
Procedure— Determine the amount of C6H12N4·C9H9NO3 dissolved by employing UV absorption, using a suitable spectrophotometer, at the wavelength of maximum absorbance at about 227 nm on filtered portions of the solution under test, suitably diluted with water, if necessary, in comparison with the Standard solution.
Tolerances— Not less than 80% (Q) of the labeled amount of C6H12N4·C9H9NO3 is dissolved in 30 minutes.
Test 2— 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 minutes.
Standard solution and Procedure— Proceed as directed for Test 1.
Tolerances— Not less than 80% (Q) of the labeled amount of C6H12N4·C9H9NO3 is dissolved in 60 minutes.USP29
Uniformity of dosage units 905: meet the requirements.
Residual solvents 467: meet the requirements.
(Official January 1, 2007)
Assay— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 700 mg of methenamine hippurate, to a 250-mL conical flask. Add 50 mL of alcohol, then add thymolphthalein TS, and titrate with 0.1 N sodium hydroxide VS. 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).
Auxiliary Information— Staff Liaison : Behnam Davani, Ph.D., MBA, Senior Scientist
Expert Committee : (MDAA05) Monograph Development-Antivirals and Antimicrobials
USP29–NF24 Page 1376
Pharmacopeial Forum : Volume No. 31(1) Page 63
Phone Number : 1-301-816-8394