Introduction

Current guidelines favour long-term, low-dose antibiotics for recurrent urinary tract infection (rUTI) prevention, but this drives antimicrobial resistance, creating an urgent need for alternatives. Methenamine Hippurate, a urinary antiseptic, shows promise, yet requires confirmation through large, rigorous trials.

Aim

To evaluate the effectiveness of Methenamine Hippurate in preventing recurrent urinary tract infections (rUTIs) in adults aged 60 years and older, including those with varying degrees of kidney function, particularly focusing on its impact on the time to UTI recurrence and its safety profile.

Patient Profile

• N=150 adults aged 60–89 years prescribed Methenamine Hippurate for UTI prophylaxis
• 88.7% were prescribed Methenamine Hippurate 1g by mouth twice daily
• Patients had documented history of ≥2 UTIs in the prior 12 months

Methods

Study endpoints

Primary:

Time to first UTI after Methenamine Hippurate initiation vs. average time between UTIs in the prior 12 months.

Secondary:

• Effectiveness in patients with CrCl <30 mL/min vs. ≥30 mL/min
• Adverse effects associated with Methenamine Hippurate 

Results

Primary Outcome

• Average time to UTI before Methenamine: 3.3 months
• Average time to UTI after Methenamine: 11.2 months (P < 0.0001)
• 22% of patients had no UTI recurrence after Methenamine initiation

UTI Characteristics

• Among post-treatment UTIs: 83.8% symptomatic, 5.1% asymptomatic
• Most common pathogen: E. coli (47%), followed by K. pneumoniae (12.8%)

Renal Function Subgroup

• Patients with CrCl <30 mL/min: time to UTI increased from 3.3 to 12.7 months (P < 0.0001)
• Patients with CrCl ≥30 mL/min: time to UTI increased from 3.3 to 11.0 months (P < 0.0001)

Figure 1: Comparison of UTI Recurrence Time Before and After Methenamine Hippurate Treatment

Adverse Events

• Occurred in 10.7% of patients
• Most common: gastrointestinal symptoms and dysuria
• Only 1 patient with CrCl <30 mL/min experienced an adverse event

Conclusion

• Methenamine Hippurate significantly increased the time to UTI in older adults with normal and reduced kidney function
• Due to lack of acquired resistance; Methenamine Hippurate may be safe prophylactic option for recurrent UTIs in older adults
• Further randomized trials are needed to confirm efficacy and safety in patients with impaired renal function

Reference

Ann Pharmacother. 2020 Apr;54(4):359-363.