UTI Prophylaxis
Recommended Prophylactic Regimen
For patients with recurrent UTIs (≥3 infections per year or ≥2 in 6 months), initiate continuous low-dose antibiotic prophylaxis with nitrofurantoin 50-100 mg daily at bedtime for 6-12 months as first-line therapy. 1
First-Line Prophylactic Options
Nitrofurantoin 50-100 mg once daily at bedtime is the preferred first-line prophylactic agent due to its low resistance rates (only 20.2% persistent resistance at 3 months and 5.7% at 9 months) and minimal disruption to protective microbiota 1, 2
Trimethoprim-sulfamethoxazole (TMP-SMX) 40 mg/200 mg (half of single-strength tablet) once daily at bedtime is an effective alternative if local resistance patterns are favorable 1, 2
Trimethoprim 100 mg once daily at bedtime can be used as monotherapy, particularly in patients who cannot tolerate sulfa drugs 1, 2
Alternative Dosing Schedules
Thrice-weekly dosing (Monday-Wednesday-Friday) with TMP-SMX 40 mg/200 mg at bedtime is equally effective as daily dosing and reduces antibiotic exposure (infection incidence of 0.1 per patient-year) 3
Post-coital prophylaxis with a single dose of nitrofurantoin 50-100 mg, TMP-SMX 40 mg/200 mg, or trimethoprim 100 mg is appropriate for women whose infections are clearly related to sexual activity 1, 4
Duration and Efficacy
Prophylaxis should continue for 6-12 months after non-antimicrobial interventions have failed 1
Continuous prophylaxis significantly reduces UTI episodes, emergency room visits, and hospital admissions (RR 0.21,95% CI 0.13-0.34 for prophylaxis versus placebo) 1, 5
Prophylaxis effectiveness is limited to the treatment period; infections commonly recur within 2.6 months after discontinuation, particularly in women with ≥3 infections in the year before prophylaxis 2
Critical Selection Considerations
Avoid fluoroquinolones for prophylaxis due to their propensity for collateral damage, resistance development, and adverse effect profiles 1
Do not use antibiotics the patient has taken in the last 6 months for prophylaxis, as resistance is more likely 1
Base selection on local antibiogram data and individual patient factors (allergies, renal function, prior resistance patterns) 1, 6
Non-Antibiotic Adjunctive Measures
Increase fluid intake to reduce infection risk 1
Vaginal estrogen for postmenopausal women has strong evidence for prevention and should be considered alongside or before antibiotic prophylaxis 1
Methenamine hippurate is a strong non-antibiotic alternative for prophylaxis in women without urinary tract abnormalities 1
Common Pitfalls to Avoid
Never treat asymptomatic bacteriuria during or after prophylaxis, as this increases antimicrobial resistance and risk of symptomatic infections 1, 6
Avoid broad-spectrum antibiotics when narrower options are available for prophylaxis 1
Do not fail to obtain urine culture before initiating treatment for breakthrough infections during prophylaxis 1
Be aware that non-E. coli infections may occur more frequently after prophylaxis discontinuation 2
Special Populations
Post-renal transplant patients most frequently receive prophylaxis (44% of prophylaxis prescriptions), typically with TMP-SMX due to dual benefit for Pneumocystis prophylaxis 5
Patients with neurogenic bladder or immobilization are more commonly prescribed nitrofurantoin 5
Patients with chronic kidney disease require dose adjustment: for creatinine clearance 15-30 mL/min, use half the usual regimen; avoid TMP-SMX if creatinine clearance is below 15 mL/min 7