Use of methenamine hippurate to prevent urinary tract infections in community adult women: a systematic review and meta-analysis

BACKGROUND: Urinary tract infections (UTIs) are often treated with antibiotics and are a source of antibiotic overuse. AIM: To systematically review randomised controlled trials (RCTs) of adult women in the community with a history of recurrent UTIs and who use methenamine hippurate prophylactically. DESIGN AND SETTING: Systematic review of women in the UK, Australia, Norway, and US (aged ≥18 years) with recurrent UTIs receiving methenamine hippurate against placebo or no treatment, and antibiotics. METHOD: The authors searched three databases, clinical trial registries, and performed forward–backward citation analysis on references of included studies. RESULTS: Six studies involving 557 participants were included (447 were analysed). Of the six studies, five were published and one was an unpublished trial record with results, three compared methenamine hippurate against placebo or control, and three compared methenamine hippurate with antibiotics. For the number of patients who remained asymptomatic, methenamine hippurate showed a non-statistically significant trend of benefit versus antibiotics over 12 months (risk ratio [RR] 0.65, 95% confidence interval [CI] = 0.40 to 1.07, I(2) 49%), versus control over 6 or 12 months (RR 0.56, 95% CI = 0.13 to 2.35, I(2) 93%), and a non-statistically significant trend versus any antibiotic for abacteruria (RR 0.80, 95% CI = 0.62 to 1.03, I(2) 23%). A similar non-statistically significant trend of benefits for methenamine hippurate for the number of UTI or bacteriuric episodes was found, and a non-statistically significant difference in the number of patients experiencing adverse events between methenamine hippurate and any comparator, with a trend towards benefit for the methenamine hippurate, was identified. Antibiotic use and resistance were not consistently reported. CONCLUSION: There is insufficient evidence to be certain of the benefits of methenamine hippurate to prevent UTI. Further research is needed to test the drug’s effectiveness in preventing UTIs and as an alternative for antibiotic treatment for UTI.