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Antiseptic drug as good as antibiotics for preventing recurrent urinary infections

Published: 10 March 2022

A new NIHR-funded study published in The BMJ, has shown the antiseptic drug methenamine hippurate is as good as antibiotics for preventing recurrent urinary tract infections in women.

Researchers led by The Newcastle upon Tyne Hospitals NHS Foundation Trust say its use as an alternative to antibiotics could also help tackle the global burden of antibiotic resistance. 

Over half of women have at least one urinary tract infection (UTI) in their lifetime and recurrence (defined as at least three repeated infections per year or two infections in the preceding six months) occurs in about a quarter of women who have one episode.

Current guidelines recommend daily low dose antibiotics as the standard preventive (prophylactic) treatment for recurrent UTI. But such long term use of antibiotics has been linked to antibiotic resistance, so research into non-antibiotic alternatives is urgently needed.

Methenamine hippurate is a drug that sterilises urine, stopping the growth of certain bacteria. Previous studies have shown that it could be effective in preventing UTIs, but the evidence is inconclusive.

The study team recruited 240 women aged 18 or over with recurrent urinary tract infections, requiring prophylactic treatment. Patients were randomly assigned to daily antibiotics or daily methenamine hippurate for 12 months, with three monthly assessments up to 18 months.

During the 12 month treatment period, the UTI rate was 0.89 episodes per person per year in the antibiotic group and 1.38 in the methenamine group - an absolute difference of just 0.49 episodes per person per year.This small difference between the two groups was less than the predefined threshold of one episode of urinary tract infection, meaning that methenamine was no worse than antibiotics at preventing urinary tract infection.

Methenamine was also associated with reduced antibiotic consumption and similar levels of adverse reactions and treatment satisfaction compared to daily antibiotics. And results were similar after further analyses, such as excluding days taking antibiotics for urinary tract infection.

Chris Harding, Chief Investigator of the study, said: “This trial provides the highest quality evidence to date detailing the clinical benefit of a non-antibiotic preventative treatment (methenamine). 

“The study demonstrates equivalent efficacy in terms of UTI prevention when methenamine is compared to the current guideline-recommended standard treatment of daily low-dose preventative antibiotics in a well-defined population of women suffering recurrent UTI episodes.”


The study was funded by the Health Technology Assessment Programme 

Find out more about the study on the NIHR Funding & Awards website.

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