“Over 50 per cent of women will suffer from a urinary tract infection in their lifetimes,” says Chris Harding at The Newcastle upon Tyne Hospitals NHS Foundation Trust. Up to a third of these women experience recurrent infections, he says, defined as at least three UTI episodes a year.
UK guidelines recommend a daily low-dose antibiotic as a preventative therapy for recurrent UTIs. However, long-term use of these drugs raises the risk of antibiotic resistance. Unlike antibiotics, which kill bacteria or prevent them from spreading, methenamine hippurate sterilises urine, inhibiting the growth of certain bacteria. The antiseptic has shown promise for UTI prevention, but the evidence is inconclusive.
To learn more, Harding and his colleagues studied 205 women who had on average six UTIs a year. Every day for 12 months, 102 of the participants took an antibiotic, while the remaining 103 were given a methenamine hippurate pill.
Over the year, those in the antibiotic group had on average 0.89 UTI episodes, compared with 1.38 episodes among those taking methenamine hippurate.
“There was basically no difference in outcomes between the two methods,” says Harding. “If we want to reduce the use of antibiotics to combat antimicrobial resistance, then trials like this provide clinicians and patients a credible non-antibiotic option for prevention.”
However, the long-term safety of methenamine hippurate is unclear. Four of the participants who took it daily were admitted to hospital as a result of a UTI, and six of the same group reported a fever during an infection. Overall, 34 people in the antibiotic group and and 35 in the antiseptic group had side effects, most of which were mild.
The study was also not blinded, so the participants and researchers were aware of the treatment received. Different antibiotics were also prescribed according to each person’s medical history, which may have affected the results.
Nevertheless, growing concerns around antibiotic resistance could make methenamine hippurate a viable preventative option if future research supports its use, a team of Australian researchers said in an editorial linked to the study.
“Hundreds of thousands of people get UTIs every year,” says Jennifer Rohn at University College London. “So it is a serious pressure point on the antimicrobial resistance crisis because so many antibiotic prescriptions are prescribed… so anything that can knock down the number of prescriptions is a good thing.”
Journal reference: The BMJ, DOI: 10.1136/bmj-2021-068229
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