Methenamine is an antibacterial agent for preventing recurrent urinary tract infection. It can be used as methenamine hippurate or methenamine mandelate preparations and is United States Food and Drug Administration-approved. Methenamine exerts its activity because it is hydrolyzed to formaldehyde in acid urine.

Hippuric Acid is an acyl glycine produced by the conjugation of benzoic acid and glycine, found as a normal component in urine as a metabolite of aromatic compounds from food. Increased urine hippuric acid content may have antibacterial effects. Hippuric Acid is used therapeutically in the form of its salts (hippurates of calcium and ammonium). It is an ingredient of FDA-approved drug Hiprex (methenamine hippurate tablets USP). Each yellow capsule-shaped tablet of Hiprex contains 1 g Methenamine Hippurate which is the Hippuric Acid Salt of Methenamine (hexamethylene tetramine). The tablet also contains inactive ingredients. Hiprex (methenamine hippurate tablets USP) has antibacterial activity because the methenamine component is hydrolyzed to formaldehyde in acid urine. Hippuric acid has some antibacterial activity and also acts to keep the urine acid. The drug is generally active against E. coli, enterococci and staphylococci. Enterobacter aerogenes is generally resistant. The urine must be kept sufficiently acid for urea-splitting organisms such as Proteus and Pseudomonas to be inhibited. Hiprex is indicated for prophylactic or suppressive treatment of frequently recurring urinary tract infections when long-term therapy is considered necessary.