What is the recommended dose of Amoxil (amoxicillin) for the treatment of bacterial sinusitis?

Amoxicillin Dosing for Bacterial Sinusitis

For adults with acute bacterial sinusitis, prescribe amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-7 days, taken at the start of meals. 1, 2

Key Diagnostic Criteria Before Prescribing

Before initiating antibiotics, confirm the diagnosis meets criteria for acute bacterial rhinosinusitis (ABRS) rather than post-viral sinusitis:

• Symptoms persisting ≥10 days without improvement, OR
• Symptoms worsening after 5-7 days following initial improvement, OR
• Severe symptoms (high fever ≥39°C, purulent nasal discharge, facial pain) for at least 3-4 consecutive days 3

Critical pitfall: Post-viral rhinosinusitis (symptoms <10 days) does not benefit from antibiotics and causes more adverse effects than benefit. 3 The European guidelines demonstrate no statistically significant improvement with antibiotics in post-viral cases, with increased diarrhea rates. 3

First-Line Dosing Regimens

Standard Adult Dosing (Preferred)

• Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-7 days 1, 2
  • Alternative: 500 mg/125 mg three times daily for 5-7 days 1, 2
  • Take at the start of meals to minimize gastrointestinal intolerance 4

Pediatric Dosing (≥3 months and <40 kg)

• 45 mg/kg/day of amoxicillin component divided every 12 hours for moderate-to-severe infections 4
• For children ≥40 kg: Use adult dosing 2

High-Dose Considerations

High-dose amoxicillin (1750-2000 mg twice daily) does NOT provide superior clinical outcomes compared to standard dosing and increases severe diarrhea rates (15.8% vs 4.8%). 5, 6 A 2021 randomized trial definitively showed no benefit at day 3 (44.3% vs 36.4% improvement, P=0.35) with similar diarrhea rates. 6

Exception: Consider high-dose amoxicillin-clavulanate (2000 mg/125 mg twice daily) only in patients with:

• Recent antibiotic use within 30 days
• Geographic areas with high penicillin-resistant S. pneumoniae prevalence (>10%)
• Immunocompromised status 1

However, even in these scenarios, the 2021 trial found no clinical benefit. 6

Treatment Duration and Monitoring

• Duration: 5-7 days for uncomplicated ABRS 1

  • Older guidelines recommended 10-14 days 3, but shorter courses show equivalent efficacy 7

• Reassess at 3-5 days: If symptoms worsen or fail to improve, consider treatment failure 1

  • Switch to respiratory fluoroquinolone (levofloxacin, moxifloxacin) if no improvement
  • Do NOT simply extend duration of same antibiotic

Renal Dosing Adjustments

For patients with severe renal impairment:

• GFR 10-30 mL/min: 500 mg/125 mg every 12 hours 2
• GFR <10 mL/min: 500 mg/125 mg every 24 hours 2
• Hemodialysis: 500 mg/125 mg every 24 hours, with additional dose during and after dialysis 2
• Do NOT use 875 mg dose if GFR <30 mL/min 2, 4

Adjunctive Therapies

Strongly recommend adding:

• Intranasal saline irrigation 1
• Intranasal corticosteroids (e.g., mometasone) 1

Avoid: Oral decongestants, antihistamines, and topical decongestants—these provide no benefit in ABRS 1

Common Pitfalls to Avoid

1. Prescribing antibiotics for symptoms <10 days: This treats viral infections unnecessarily and increases antibiotic resistance 3

2. Using two 250 mg/125 mg tablets instead of one 500 mg/125 mg tablet: These are NOT equivalent due to different clavulanate ratios 2

3. Prescribing high-dose formulations routinely: Recent high-quality evidence shows no benefit with increased adverse effects 5, 6

4. Extending treatment beyond 7 days without reassessment: If not improving by day 3-5, change antibiotics rather than extending duration 1

5. Ignoring renal function: The 875 mg dose is contraindicated in severe renal impairment 2, 4