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

Abstract

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.

Keywords::

• antiseptic
• methenamine
• prevention
• recurrent urinary tract infection
• resistance

Disclaimer

This material is the result of work supported with resources and the use of facilities at the Fargo VA Medical Center. The contents do not represent the views of the Department of Veterans Affairs or the United States Government.

Financial & competing interests disclosure

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Methenamine has been prescribed as a urinary antiseptic for almost 100 years but is often forgotten or overlooked by clinicians.

• Methenamine is a urinary antibacterial agent that can be used in either methenamine hippurate or methenamine mandelate preparations.

• Formaldehyde, the main product of methenamine in an acidic environment, exhibits its nonspecific antibacterial activity by denaturing proteins and nucleic acid of bacteria.

• Because formaldehyde is an antiseptic and not an antibiotic, bacteria are unlikely to be resistant to formaldehyde in an acidic environment and in adequate concentration.

• Methenamine has been shown to be effective in suppressing or preventing recurrent lower urinary tract infections.

• Methenamine should be considered when the more commonly used antibiotics fail to suppress recurrent urinary tract infections, or there is limitation due to adverse events with other preventive therapies.

• This forgotten antiseptic will become more important as bacteria continue to become resistant to antibiotics.