About this trial
This open-label, parallel-group randomized controlled trial compares two prophylaxis strategies for recurrent urinary tract infection (rUTI) in postmenopausal women: (1) nightly oral nitrofurantoin 100 mg for 6 months versus (2) a vaginal tablet containing Lactobacillus with ultra-low-dose estriol (Gynoflor: nightly for 14 days, then twice weekly to month 6). Participants (≥40 years) are randomized 1:1 in computer-generated blocks and followed for 6 months. The primary endpoint is the proportion with rUTI recurrence within 6 months. Secondary endpoints include time to first recurrence, antibiotic resistance in breakthrough infections, change in lower urinary tract symptoms (Thai RUTISS), and urinary microbiome measures (Lactobacillus dominance and community diversity by qPCR and 16S rRNA). Key assessments occur at baseline and month 6 (urinalysis, culture, urinary microbiome sampling, and kidney function). Adherence and adverse events are captured via twice-weekly phone/Line contacts. Approximately 100 participants (50 per arm) will be enrolled as a feasibility-sized pilot.
Eligibility criteria
Qualifiers
Female, postmenopausal, age ≥40 years
Clinical history of recurrent urinary tract infection (rUTI) as assessed by the investigator
Able and willing to take assigned prophylaxis for 6 months
Able to attend baseline and Month 6 study visits and provide urine samples
Disqualifiers
Current symptomatic UTI at enrollment (may be treated and reconsidered after resolution)
Known hypersensitivity or contraindication to nitrofurantoin or to the Lactobacillus/estriol vaginal tablet (Gynoflor) or their excipients; significant renal impairment or other label-based contraindications to nitrofurantoin per local practice
Planned urologic surgery or procedure expected during the 6-month study period
Recent bacterial vaginosis (e.g., within the past month) or active vulvovaginal skin disorders precluding vaginal product use
Trial design
Treatments tested in this trial
- Nitrofurantoin
- Gynoflor