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

Amoxicillin Dosing and Duration for Bacterial Sinusitis

For adults with acute bacterial sinusitis, amoxicillin 500 mg twice daily for 5-10 days is the recommended first-line treatment, with high-dose amoxicillin 875 mg twice daily reserved for severe infections or areas with high antibiotic resistance. 1, 2

Adult Dosing Recommendations

Standard-dose amoxicillin:

• 500 mg twice daily for mild to moderate infections 1
• Appropriate for patients without recent antibiotic exposure (within 4-6 weeks) 1, 2
• Provides adequate coverage against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis 2

High-dose amoxicillin:

• 875 mg twice daily for severe infections 1, 3
• Indicated in communities with high prevalence of penicillin-resistant S. pneumoniae (>10-15% resistance) 2
• Required for patients with recent antibiotic use within 4-6 weeks 2
• Should be used when severe symptoms are present (fever ≥39°C with purulent discharge for ≥3 days) 4, 1

Pediatric Dosing Recommendations

Standard-dose amoxicillin:

• 45 mg/kg/day divided into 2 doses for children ≥3 months with uncomplicated disease 4, 5
• Appropriate for children >2 years, not in daycare, without recent antibiotic exposure 2, 5

High-dose amoxicillin:

• 80-90 mg/kg/day divided into 2 doses for high-risk children 4, 5
• Risk factors include: age <2 years, daycare attendance, antibiotic use within past 4-6 weeks, or high local resistance rates 4, 5
• Maximum dose should not exceed adult dosing 3

Special consideration for infants <12 weeks:

• Maximum 30 mg/kg/day divided every 12 hours due to immature renal function 3

Treatment Duration

The optimal duration is 5-10 days for uncomplicated acute bacterial sinusitis, with most guidelines recommending treatment until symptom-free for 7 days (typically 10-14 days total). 1, 2

• Shorter 5-7 day courses have comparable efficacy with fewer side effects for uncomplicated maxillary sinusitis 1, 6
• Traditional 10-14 day courses remain standard in most guidelines, though evidence supports shorter duration 1, 2, 7
• Minimum 10 days required for Streptococcus pyogenes infections to prevent acute rheumatic fever 4, 3
• Continue treatment for 48-72 hours beyond symptom resolution 3

When to Escalate to Amoxicillin-Clavulanate

Switch to high-dose amoxicillin-clavulanate (875 mg/125 mg twice daily for adults; 90 mg/kg/day amoxicillin component for children) if no improvement after 72 hours. 4, 1, 5

The clavulanate component provides coverage against β-lactamase-producing organisms (H. influenzae and M. catarrhalis), which account for treatment failures 1, 2

Amoxicillin-clavulanate as first-line therapy is indicated when:

• Recent antibiotic exposure within 4-6 weeks 1, 2
• High local prevalence of β-lactamase-producing organisms 2
• Severe disease presentation 1
• Age <2 years or daycare attendance 5

Critical Pitfalls to Avoid

Reassess at 72 hours (pediatrics) or 3-5 days (adults):

• Only 9% of placebo-treated children improve between days 3-10 after failing at day 3 5
• Failure to improve suggests β-lactamase-producing organisms or resistant S. pneumoniae 1, 5
• Do not continue ineffective therapy beyond this timepoint 4, 5

Avoid inadequate dosing:

• Standard-dose amoxicillin may be insufficient in areas with >10-15% penicillin-resistant S. pneumoniae 2
• High-dose formulations (80-90 mg/kg/day in children; 875 mg twice daily in adults) are necessary for resistant organisms 1, 2

Complete the full course:

• Relapse rates within one month are 7.7% even after successful therapy 7
• Premature discontinuation increases risk of treatment failure 1

Renal dosing adjustments:

• Patients with GFR <30 mL/min should NOT receive 875 mg dosing 3
• For GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours 3
• For GFR <10 mL/min: 500 mg or 250 mg every 24 hours 3

Penicillin-Allergic Patients

For non-severe penicillin allergy, second- or third-generation cephalosporins (cefuroxime, cefpodoxime, cefdinir) are preferred alternatives. 1, 2

• Cross-reactivity risk with cephalosporins is negligible for non-Type I reactions 1
• Avoid azithromycin due to 20-25% resistance rates 1, 2
• Reserve fluoroquinolones (levofloxacin, moxifloxacin) for treatment failures or severe Type I hypersensitivity 1

Adjunctive Therapy

Intranasal corticosteroids should be added to antibiotic therapy to reduce mucosal inflammation and improve symptom resolution 1

• Short-term oral corticosteroids may be considered for marked mucosal edema or severe pain 1
• Supportive measures include adequate hydration, analgesics, and sleeping with head elevated 1