What prophylactic antibiotic should be given to a patient with recurrent Urinary Tract Infections (UTIs) and a currently negative urine dipstick (urine dip) result?

Prophylactic Antibiotic Recommendations for Recurrent UTIs with Negative Urine Dipstick

For a patient with recurrent UTIs requiring hospitalization but currently negative urine dipstick, continuous or postcoital antimicrobial prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMX) 160/800 mg three times weekly is recommended as first-line prophylactic therapy after non-antimicrobial interventions have been tried. 1

Diagnostic Considerations

• A negative urine dipstick does not rule out recurrent UTIs, especially between active infections 1
• Recurrent UTIs are defined as ≥3 UTIs per year or ≥2 UTIs in the last 6 months 1
• Confirm diagnosis with urine culture during symptomatic episodes, not during asymptomatic periods 1
• Patients requiring hospitalization for UTIs should be considered to have complicated or severe infections 1

Treatment Algorithm

Step 1: Non-antimicrobial interventions (try these first)

• For postmenopausal women: vaginal estrogen replacement (strong recommendation) 1
• Immunoactive prophylaxis products (strong recommendation) 1
• Methenamine hippurate (strong recommendation for women without urinary tract abnormalities) 1
• Increased fluid intake (weak recommendation but minimal risk) 1
• Consider cranberry products (weak recommendation) 1
• Consider probiotics with proven efficacy (weak recommendation) 1

Step 2: Antimicrobial prophylaxis (if non-antimicrobial interventions fail)

• First-line option: Trimethoprim-sulfamethoxazole 160/800 mg three times weekly 1, 2
• Alternative options:
  • Nitrofurantoin 50-100 mg daily (avoid in renal impairment) 1
  • Trimethoprim 100 mg daily 3, 4
  • Cephalexin 250 mg daily 1
  • Fosfomycin 3g every 10 days 1

Special Considerations

• For UTIs associated with sexual activity: postcoital prophylaxis with TMP-SMX 160/800 mg or nitrofurantoin 50-100 mg taken within 2 hours after intercourse 1
• For patients with good compliance: self-administered short-term therapy at onset of symptoms 1
• Duration of prophylaxis typically ranges from 6-12 months 1

Important Caveats

• Monitor for adverse effects of TMP-SMX including rash, gastrointestinal disturbances 1
• Avoid TMP-SMX in first and last trimesters of pregnancy 1
• Consider local resistance patterns - TMP-SMX resistance rates may reach 19.3% in recurrent UTIs 5
• Nitrofurantoin has rare but serious risks of pulmonary and hepatic toxicity (0.001% and 0.0003% respectively) 1
• Rotating antibiotics every 3 months may help prevent development of resistance 1
• Avoid treating asymptomatic bacteriuria as this increases antibiotic resistance 1

Monitoring

• Periodic reassessment of prophylaxis effectiveness and adverse effects 1
• Consider urine culture if symptoms recur during prophylaxis 1
• Do not perform routine post-treatment urinalysis or cultures in asymptomatic patients 1