Methenamine: a forgotten drug for preventing recurrent urinary tract infection in a multidrug resistance era.

In the era of multidrug resistance, it is critical to utilize antibiotics in an appropriate manner and to identify new treatments or revisit the use of 'forgotten' drugs. Because urinary tract infections (UTIs) are common, particularly in an increasing elderly population, the 'forgotten' drug, methenamine, may become important as a preventive therapy for recurrent UTIs. Methenamine, a urinary antibacterial agent, can be used as methenamine hippurate or methenamine mandelate preparations and is United States Food and Drug Administration-approved. This article discusses the place of preventive therapy for recurrent UTIs, chemistry, mechanism of action, pharmacology, clinical uses, dosage, adverse reactions and safety, and drug interactions of methenamine. Because of its unique antiseptic property, the authors suggest that methenamine should be considered when more commonly used antibiotics fail to suppress recurrent UTIs.