What are the recommended antibiotics for treating urinary tract infections (UTIs)?

Recommended Antibiotics for Urinary Tract Infections (UTIs)

For uncomplicated UTIs in women, first-line treatment options include fosfomycin trometamol (3g single dose), nitrofurantoin (100mg twice daily for 5 days), or pivmecillinam (400mg three times daily for 3-5 days). 1

Treatment Algorithm for UTIs

Uncomplicated Cystitis in Women

1. First-line options:

   • Fosfomycin trometamol: 3g single dose (1 day)
   • Nitrofurantoin macrocrystals: 100mg twice daily for 5 days
   • Pivmecillinam: 400mg three times daily for 3-5 days

2. Alternative options (when first-line agents cannot be used):

   • Cephalosporins (e.g., cefadroxil): 500mg twice daily for 3 days (if local E. coli resistance <20%)
   • Trimethoprim: 200mg twice daily for 5 days (avoid in first trimester of pregnancy)
   • Trimethoprim-sulfamethoxazole: 160/800mg twice daily for 3 days (avoid in last trimester of pregnancy) 1, 2

UTIs in Men

• Trimethoprim-sulfamethoxazole: 160/800mg twice daily for 7 days
• Fluoroquinolones: According to local susceptibility testing
• Nitrofurantoin: 100mg twice daily for 7 days 1, 2

Special Considerations

Antimicrobial Resistance

• Local resistance patterns should guide empiric therapy
• Trimethoprim-sulfamethoxazole should only be used when local E. coli resistance is <20% 3, 4
• Fluoroquinolones should be reserved for more invasive infections due to increasing resistance and FDA warnings about serious adverse effects 5, 3

Pregnancy

• Avoid trimethoprim in the first trimester
• Avoid trimethoprim-sulfamethoxazole in the last trimester 1, 6

Renal Impairment

• Nitrofurantoin is contraindicated in patients with CrCl <60 mL/min 5
• For trimethoprim-sulfamethoxazole:
  • CrCl >30 mL/min: Standard regimen
  • CrCl 15-30 mL/min: Half the usual regimen
  • CrCl <15 mL/min: Not recommended 6

Treatment Failure

• If symptoms don't resolve by the end of treatment or recur within 2 weeks:
  • Obtain urine culture with antimicrobial susceptibility testing
  • Assume the organism is not susceptible to the initial agent
  • Retreat with a 7-day regimen using a different antibiotic 1

Recurrent UTIs

Definition

• At least three UTIs per year or two UTIs in the last 6 months 1

Prevention Strategies

• Non-antimicrobial approaches:

  • Increased fluid intake for premenopausal women
  • Vaginal estrogen replacement for postmenopausal women (strong recommendation)
  • Methenamine hippurate (strong recommendation)
  • Immunoactive prophylaxis (strong recommendation)
  • Probiotics, cranberry products, D-mannose (weak recommendations) 1, 5

• Antimicrobial prophylaxis:

  • Consider when non-antimicrobial interventions have failed
  • Options include continuous or post-coital prophylaxis
  • Self-administered short-term therapy for patients with good compliance 1, 5

Complicated UTIs and Pyelonephritis

For complicated UTIs requiring parenteral therapy, options include:

• Meropenem: 1g IV every 8 hours
• Ciprofloxacin: 400mg IV twice daily
• Ceftriaxone: 1-2g IV daily
• Piperacillin/tazobactam: 2.5-4.5g IV three times daily 5

Pitfalls and Caveats

1. Diagnostic testing: Urine culture is not needed for uncomplicated UTIs in women with typical symptoms but should be obtained for:

   • Suspected pyelonephritis
   • Symptoms that don't resolve or recur within 4 weeks after treatment
   • Women with atypical symptoms
   • Pregnant women 1

2. Antibiotic stewardship: Reserve broad-spectrum antibiotics (carbapenems, fluoroquinolones) for complicated infections to prevent resistance development 5, 3

3. Treatment duration: Shorter courses (1-5 days) are appropriate for uncomplicated cystitis in women, while men typically require 7 days of treatment 1, 2

4. Pharmacokinetic considerations: Beta-lactam antibiotics' efficacy depends on time above MIC, while fluoroquinolones and aminoglycosides depend on peak/MIC or AUC/MIC ratios 7

5. Post-treatment follow-up: Routine post-treatment urinalysis or cultures are not indicated for asymptomatic patients 1