Methenamine does not have antibacterial properties in an alkaline environment (pH≥6); however, in a more acidic environment (pH<6), methenamine is hydrolyzed to formaldehyde. (1) Formaldehyde is considered to be highly bactericidal. (1) Formaldehyde has nonspecific antibacterial activity and works by denaturing proteins and nucleic acid of bacteria. (1) Certain bacteria such as Proteus sp. can alkalize urine, inhibiting the beneficial activity of formaldehyde. (1) The key role of the salt component of the drug, for example hippuric acid, is to maintain the acidic state of the urine. (1)