ABSTRACT
Methenamine was introduced into clinical practice as a urinary antiseptic as long ago as 1894. The antiseptic action of this cyclic hydrocarbon depends on its chemical breakdown by hydrolysis to formaldehyde and ammonia. This process takes place in the urine, to a significant degree only when the urine is acidic. In vitro studies have suggested that an effective concentration of formaldehyde with recommended doses is likely to be achieved only if the urine pH is less than 5.7–5.85 (Musher and Griffith, 1974). The drug is thereby entirely dependent for its effect on proper acidification of the urine (Kass, 1955). Formaldehyde is not released while methenamine circulates in the blood.
