d-Mannose for Recurrent Urinary Tract Infection Prevention in Postmenopausal Women Using Vaginal Estrogen: A Randomized Controlled Trial.

IMPORTANCE: Further research is needed to determine whether d-mannose plus vaginal estrogen therapy (VET) is beneficial over VET alone for recurrent urinary tract infection (rUTI) prevention. OBJECTIVE: The aim of this study was to evaluate d-mannose efficacy for rUTI prevention in postmenopausal women using VET. STUDY DESIGN: We conducted a randomized controlled trial comparing d-mannose (2 g/d) with control. Participants were required to have a history of uncomplicated rUTIs and to remain on VET throughout the trial. They were followed up 90 days for incident UTIs. Cumulative UTI incidences were calculated by the Kaplan-Meier method and compared by Cox proportional hazards regression. For the planned interim analysis, P < 0.001 was considered statistically significant. Futility analysis was performed by generating post hoc conditional power for multiple scenarios. RESULTS: We evaluated 545 patients for frequent/recurrent UTIs from March 1, 2018, to January 18, 2020. Of these women, 213 had culture-proven rUTIs, 71 were eligible, 57 enrolled, 44 began their planned 90-day study period, and 32 completed the study. At interim analysis, the overall cumulative UTI incidence was 46.6%; 41.1% in the treatment arm (median time to first UTI, 24 days) and 50.4% in the control arm (median, 21 days); hazard ratio, 0.76; 99.9% confidence interval, 0.15-3.97. d-Mannose was well tolerated with high participant adherence. Futility analysis suggested the study lacked power to detect the planned (25%) or observed (9%) difference as statistically significant; the study was halted before conclusion. CONCLUSIONS: d-Mannose is a well-tolerated nutraceutical, but further research is needed to determine whether d-mannose in combination with VET has a significant, beneficial effect beyond VET alone in postmenopausal women with rUTIs.