What is the recommended dose of amoxicillin for treating bacterial sinusitis?

Recommended Amoxicillin Dosage for Bacterial Sinusitis

For treating bacterial sinusitis in adults, amoxicillin should be prescribed at 500 mg twice daily, while children should receive 45 mg/kg twice daily. 1

Adult Dosing Options

First-Line Treatment

• Standard-dose amoxicillin: 500 mg twice daily for 5-7 days 1, 2
• High-dose amoxicillin: Consider in areas with high pneumococcal resistance
  • 875 mg twice daily for 5-7 days 2
  • Up to 1.0 g every 12 hours in areas with high penicillin resistance 1

Alternative First-Line Option

• Amoxicillin-clavulanate: 875/125 mg twice daily for 5-7 days 2
  • Preferred in patients with:
    • Recent antibiotic use
    • Treatment failure with amoxicillin
    • High risk for resistant organisms

Pediatric Dosing

• Standard-dose amoxicillin: 45 mg/kg twice daily 1
• High-dose amoxicillin: 90 mg/kg/day in 2 divided doses for areas with high pneumococcal resistance 1

When to Consider High-Dose Therapy

Consider high-dose therapy in patients with:

• Age <2 or >65 years
• Recent antibiotic use
• Recent hospitalization
• Comorbidities
• Immunocompromised state
• Daycare attendance (pediatric patients)
• Areas with high prevalence of penicillin-resistant S. pneumoniae (>25-50% of strains) 1

Treatment Duration and Assessment

• Standard treatment duration: 5-7 days 2
• Assess for clinical improvement within 72 hours of starting antibiotics 2
• If no improvement after 3-5 days, consider switching to a broader-spectrum antibiotic 2

Clinical Evidence and Considerations

Recent research comparing standard-dose vs. high-dose amoxicillin/clavulanate shows mixed results:

• A 2021 study found no significant benefit of high-dose over standard-dose amoxicillin/clavulanate at day 3 (44.3% vs. 36.4% improvement) 3
• However, a 2018 study showed that immediate-release high-dose amoxicillin/clavulanate provided more rapid improvement than standard-dose (52.4% vs. 34.4%), but with increased risk of severe diarrhea (15.8% vs. 4.8%) 4

Important Caveats

• Antibiotic resistance: S. pneumoniae resistance to penicillin has been increasing, with 25-50% of strains showing resistance 1
• Adverse effects: Monitor for gastrointestinal side effects, particularly diarrhea, which is more common with higher doses 3, 4
• Inappropriate use: Antibiotics should not be used for uncomplicated viral upper respiratory tract infections 1
• Diagnostic criteria: Only prescribe antibiotics when bacterial sinusitis is likely, as indicated by:
  • Persistent symptoms (>10 days without improvement)
  • Severe symptoms (high fever ≥39°C with purulent discharge for ≥3 days)
  • Worsening symptoms after initial improvement ("double-sickening") 2

Alternative Antibiotics

For patients with penicillin allergy or treatment failure:

• Cephalosporins: Cefuroxime (250-500 mg BID), cefpodoxime (200-400 mg BID)
• Fluoroquinolones (adults only): Levofloxacin (500 mg daily), moxifloxacin (400 mg daily)
• Macrolides: Less recommended due to increasing resistance patterns 1, 2