What antibiotics are used to treat urinary tract infections (UTIs)?

Antibiotic Treatment for Urinary Tract Infections

For lower urinary tract infections (cystitis), first-line antibiotics include amoxicillin-clavulanic acid, sulfamethoxazole-trimethoprim, or nitrofurantoin, while ciprofloxacin is recommended for pyelonephritis and prostatitis. 1

Lower Urinary Tract Infections (Cystitis)

First-line options:

• Amoxicillin-clavulanic acid (Access category)
• Sulfamethoxazole-trimethoprim (Access category)
  • Dosage: 160/800 mg (1 DS tablet) twice daily for 3 days in uncomplicated cases 2
  • Not recommended for patients under 2 months of age 2
• Nitrofurantoin (Access category)
  • Dosage: 100 mg twice daily for 5 days 3
  • Maintains high susceptibility against E. coli urinary isolates 1

Second-line options:

• Fosfomycin was excluded from WHO recommendations based on comparative trials showing nitrofurantoin's superior clinical and microbiological resolution 1
• Fluoroquinolones (e.g., ciprofloxacin) should be reserved for more invasive infections due to resistance concerns and FDA safety warnings about serious side effects affecting tendons, muscles, joints, and the nervous system 1, 3

Upper Urinary Tract Infections (Pyelonephritis and Prostatitis)

Mild to moderate cases:

• First choice: Ciprofloxacin (Watch category) - if local resistance patterns permit 1
• Second choice: Ceftriaxone or cefotaxime (Watch category) 1

Severe cases:

• First choice: Ceftriaxone or cefotaxime (Watch category) 1
• Second choice: Amikacin (Access category) - preferred over gentamicin due to better resistance profile 1

Special Considerations

Antimicrobial Resistance

• Global surveillance data shows approximately 75% of E. coli urinary isolates are resistant to amoxicillin alone, which is why it's not recommended as monotherapy 1
• Amoxicillin-clavulanic acid and nitrofurantoin maintain high susceptibility against common uropathogens 1

Patient-Specific Factors

• Renal impairment: For sulfamethoxazole-trimethoprim, reduce dosage when creatinine clearance is 15-30 mL/min; avoid when below 15 mL/min 2
• Enterococcus faecalis infections: Consider fosfomycin (3g single dose) for uncomplicated UTIs caused by ESBL-producing organisms 4

Duration of Therapy

• Uncomplicated cystitis in women: 3-5 days for sulfamethoxazole-trimethoprim, 5-7 days for nitrofurantoin 3
• Pyelonephritis: 10-14 days 5

Clinical Pearls and Pitfalls

• Pitfall: Using fluoroquinolones as first-line therapy for uncomplicated UTIs. These should be reserved for more serious infections due to increasing resistance rates and safety concerns 1, 6

• Pitfall: Using amoxicillin alone for empiric treatment. High resistance rates (median 75%) make this ineffective as monotherapy 1

• Pearl: When choosing empiric therapy, consider local resistance patterns, patient's risk factors for resistance, and recent antibiotic exposure 6

• Pearl: Nitrofurantoin is particularly effective for lower UTIs due to its concentrated action in the urinary tract and low resistance rates, but should not be used for pyelonephritis or systemic infections 7

By following these evidence-based recommendations, clinicians can optimize treatment outcomes while minimizing the risk of antimicrobial resistance in patients with urinary tract infections.