BERKELEY, CA (UroToday.com) - In this era of multidrug resistance and drastic decrease in drug development targeting bacterial infections, it is critical that clinicians strive to utilize antibiotics judiciously. Thus, it is timely to revisit the use of ‘forgotten’ drugs such as methenamine, a urinary antiseptic agent, in preventing recurrent urinary tract infections (UTI). Methenamine can be used as either methenamine hippurate or methenamine mandelate and is approved by the FDA to prevent recurrent lower UTIs with no renal tract abnormalities, but should not be used to suppress infections outside the urinary bladder such as pyelonephritis or chronic prostatitis.
Related adverse reactions have been reported in less than 4% of patients receiving the drug and the Cochrane Collaboration Review reported that nausea and diarrhea were the most common adverse events. Exceeding the recommended dose (eight grams daily for 3-4 weeks) can lead to bladder irritation and is related to the high concentration of formaldehyde in the urine. Dysuria may improve by reducing the dose and/or acidifying the urine.
To date, studies with methenamine have been fairly limited, and quality of the studies has been mixed. Studies have differed on the doses of methenamine used (with some studies co-administering acidification agents with methenamine while others did not), some studies had limited follow ups, studies had a quite heterogeneous population, and even the definition of UTI was not well reported in a few of the trials. Therefore, the ability to interpret measures of outcome has been difficult. We believe there is a need for further large, randomized controlled clinical trials to clarify these questions.
It is surprising that many clinicians do not know about this drug and its potential for preventing UTI in patients without renal tract abnormalities, particularly when used for short term prophylaxis. The rate of reported adverse events is low, and its use is unlikely to lead to any harm.
Kimberly D. Hammer, PhD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Research & Development Coordinator, Fargo VA Health Care System
Assistant Professor, University of North Dakota School of Medicine & Health Sciences