For recurrent UTIs, a non-antibiotic pill matched daily antibiotics in a trial

Women who get urinary tract infections over and over are often offered a daily low-dose antibiotic to hold them off — a regimen that works but keeps a person on antibiotics for months or years. A large UK trial found that a non-antibiotic alternative, methenamine hippurate, prevented recurrences about as well over 12 months, meeting a pre-agreed bar for non-inferiority [s1]. That is a real result, but it sits against a wider evidence base for recurrent-UTI prevention that a recent review describes as thin and often contradictory [s2].

What the trial did

The ALTAR trial recruited women aged 18 and over with recurrent urinary tract infections requiring preventive treatment, across eight UK centres between June 2016 and June 2018 [s1]. It randomly assigned 240 of them, in equal groups, to either daily antibiotic prophylaxis (n=120) or methenamine hippurate (n=120) for 12 months — an open-label design, meaning both patients and clinicians knew which treatment was given, and crossover between arms was allowed [s1].

The measure that mattered was how many symptomatic, antibiotic-treated UTIs occurred during the treatment year. In the analysis of the 205 women (85%) followed for at least six months, the incidence was 0.89 episodes per person-year (95% confidence interval 0.65 to 1.12) in the antibiotic group and 1.38 (1.05 to 1.72) in the methenamine group [s1]. The absolute difference was 0.49 episodes per person-year (90% CI 0.15 to 0.84) [s1].

The key to reading that difference is the trial's non-inferiority margin — the largest gap the researchers would accept while still calling the two treatments equivalent. It was set at one episode of UTI per person-year, and, notably, that threshold was chosen not by statisticians but by a patient and public involvement group asked what size of difference would matter to them [s1]. Because the difference came in under that margin, methenamine was declared non-inferior [s1]. Adverse reactions were similar and mostly mild: 24% (34 of 142) in the antibiotic group and 28% (35 of 127) in the methenamine group [s1].

Why this matters beyond one drug

Recurrent-UTI prevention has become a case study in antibiotic stewardship — the effort to reduce antibiotic use so bacteria stay treatable. The ALTAR authors frame their finding in exactly those terms: methenamine hippurate "might be appropriate" for women with recurrent UTIs, informed by patient preference and the goal of using fewer antibiotics, given that it was non-inferior to daily prophylaxis [s1]. The trial does not say methenamine is better, and it does not say every woman should switch. It says a non-antibiotic option is a defensible choice, which is a narrower and more useful claim.

The rest of the prevention menu is weakly evidenced

Beyond prophylactic drugs, the advice women actually receive — drink more water, urinate after sex, try cranberry, take a supplement — varies widely in how well it is supported. A 2026 scoping review set out to map the preventive strategies recommended for recurrent UTIs in premenopausal women, screening 6,170 records and including 78 publications of reviews, guidelines and expert reports published between 2013 and 2023 [s2]. Its conclusion was blunt: alongside the well-studied approaches of antibiotic regimens and cranberry products, the review found less-studied strategies including behavioural changes, vitamin supplements and increased hydration, and reported that recommendations were "often unsupported by evidence" and that disagreement among sources was common [s2].

That is the honest state of the field. Some prevention strategies have trials behind them; many of the ones passed along as common sense do not, and the guidance itself does not agree with itself. The site covers the specific case of cranberry separately.

What the evidence does not settle

ALTAR was an open-label trial, which can inflate reported benefit for whichever arm patients expect to work, and it was conducted in women referred for preventive treatment — not the average person with an occasional infection [s1]. It measured prevention over a year, not cure of an active infection, and it does not address recurrent UTIs in postmenopausal women, in whom the drivers and options differ. The scoping review, for its part, maps the evidence rather than generating new trial data, and its central message is precisely that the trials needed to guide most of this advice have not been done [s2].

The liftable summary: for women weighing long-term antibiotics against a non-antibiotic alternative, methenamine hippurate has a solid non-inferiority trial behind it — and most of the other things people are told to do to prevent recurrent UTIs do not.

This article is informational and is not medical advice. Preventive treatment for recurrent urinary tract infections should be decided with a clinician.