Amoxicillin-Clavulanate Dosing for UTI
For uncomplicated cystitis in women, use amoxicillin-clavulanate 500 mg/125 mg every 8 hours or 875 mg/125 mg every 12 hours for 3-7 days, though this is NOT a first-line agent and should only be used when nitrofurantoin, trimethoprim-sulfamethoxazole, or fosfomycin cannot be used. 1
First-Line vs. Alternative Therapy
- Amoxicillin-clavulanate is explicitly NOT first-line for uncomplicated UTI because beta-lactams have inferior efficacy compared to fluoroquinolones and trimethoprim-sulfamethoxazole, with clinical cure rates as low as 58% versus 77% for ciprofloxacin 2
- Reserve amoxicillin-clavulanate for situations where first-line agents (nitrofurantoin, trimethoprim-sulfamethoxazole if local resistance <20%, or fosfomycin) cannot be used due to allergy, intolerance, or resistance 1
- Beta-lactams cause more adverse effects than other UTI antimicrobials 1
Dosing by Clinical Scenario
Uncomplicated Cystitis (Women)
- 500 mg/125 mg every 8 hours OR 875 mg/125 mg every 12 hours for 3-7 days 1
- The 7-day duration is supported by strong evidence (A-III rating) 2
Complicated UTI or Pyelonephritis
- 875 mg/125 mg every 12 hours for 7-14 days 2
- Use 7 days for patients with prompt symptom resolution who have been afebrile for at least 48 hours 2
- Extend to 10-14 days for delayed response 2
- For males, use 14 days when prostatitis cannot be excluded 2
- Consider an initial IV dose of ceftriaxone 1g or aminoglycoside before transitioning to oral amoxicillin-clavulanate for pyelonephritis, as beta-lactams are less effective than fluoroquinolones for upper tract infections 1
Catheter-Associated UTI
- 7 days for prompt symptom resolution, 10-14 days for delayed response 2
- Replace the catheter before starting antibiotics if it has been in place for ≥2 weeks 2
Pediatric UTI (Ages 2-24 Months)
- 20-40 mg/kg/day divided into 3 doses 3
- Total course should be 7-14 days 3
- Do NOT use nitrofurantoin in febrile infants, as it doesn't achieve adequate parenchymal concentrations 3
Critical Pitfalls to Avoid
- NEVER use plain amoxicillin or ampicillin empirically for UTI due to high worldwide resistance rates 1
- Always obtain urine culture before starting antibiotics in complicated UTIs due to wide spectrum of organisms and increased antimicrobial resistance 2
- Verify susceptibility for Klebsiella infections, as ESBL-producing strains may require alternative therapy (though high-dose amoxicillin-clavulanate 2875 mg twice daily has shown success in select ESBL cases) 2, 4
- Address underlying urological abnormalities (obstruction, foreign bodies, incomplete voiding) as these mandate longer treatment 2
- Consider local resistance patterns when selecting empiric therapy 2
FDA-Approved Dosing Data
The FDA label confirms that 875 mg/125 mg every 12 hours is comparable in efficacy to 500 mg/125 mg every 8 hours for lower respiratory tract infections and complicated UTIs, with significantly lower rates of severe diarrhea (1% vs 2%) 5. Bacteriologic efficacy rates at 2-4 days post-therapy were 81% for the every 12 hours regimen versus 80% for the every 8 hours regimen 5.