What is the recommended treatment for acute bacterial sinusitis?

Treatment of Acute Bacterial Sinusitis

First-Line Antibiotic Selection

For adults with acute bacterial sinusitis, amoxicillin-clavulanate 875 mg/125 mg twice daily is the preferred first-line antibiotic, not amoxicillin alone. 1, 2

The rationale for preferring amoxicillin-clavulanate over plain amoxicillin relates to increasing prevalence of β-lactamase-producing Haemophilus influenzae and Moraxella catarrhalis since introduction of pneumococcal conjugate vaccines. 3 However, plain amoxicillin 500 mg twice daily (for mild disease) or 875 mg twice daily (for moderate disease) remains acceptable for uncomplicated cases without recent antibiotic exposure. 1

Pediatric Dosing

• Standard therapy: Amoxicillin 45 mg/kg/day in 2 divided doses for children without recent antibiotic use 1
• High-dose therapy: Amoxicillin-clavulanate 80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses for children with risk factors (age <2 years, daycare attendance, recent antibiotic use within 4-6 weeks) or areas with high prevalence of resistant S. pneumoniae 3, 1

Treatment Duration

The standard duration is 5-10 days for adults, with most guidelines recommending treatment until symptom-free for 7 days. 1, 2 For children, the American Academy of Pediatrics recommends 10-14 days. 1 Shorter 5-7 day courses have comparable efficacy with fewer side effects. 1

Penicillin-Allergic Patients

For patients with documented penicillin allergy, second- or third-generation cephalosporins are the preferred alternatives, as the risk of cross-reactivity is negligible. 1

Recent evidence demonstrates that the risk of serious allergic reactions to second- and third-generation cephalosporins in penicillin-allergic patients is almost nil and no greater than the risk among patients without such allergy. 3, 1

Specific Options for Penicillin Allergy:

• Second-generation: Cefuroxime-axetil 3, 1
• Third-generation: Cefpodoxime-proxetil, cefdinir, or cefprozil 3, 1
• For severe beta-lactam allergy: Levofloxacin 500 mg once daily for 10-14 days (reserve for true contraindications to beta-lactams) 1

Critical pitfall: Azithromycin and other macrolides should NOT be used as first-line therapy due to 20-25% resistance rates among S. pneumoniae and H. influenzae. 1, 4

Treatment Failure Protocol

Reassess patients at 72 hours (pediatrics) or 3-5 days (adults) if no improvement occurs. 3, 1

If the patient fails initial therapy or shows worsening symptoms:

• Switch to high-dose amoxicillin-clavulanate: 90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses (pediatrics) or 2 g amoxicillin every 12 hours (adults) 1
• Alternative for treatment failure: Respiratory fluoroquinolones (levofloxacin 500-750 mg once daily or moxifloxacin 400 mg once daily) provide 90-92% predicted clinical efficacy and excellent coverage against multi-drug resistant S. pneumoniae 1, 5

The failure of initial therapy may be due to β-lactamase-producing organisms (H. influenzae or M. catarrhalis) or drug-resistant S. pneumoniae. 1

Fluoroquinolone Use: When and Why

Reserve fluoroquinolones for specific situations to prevent resistance development—do not use as routine first-line therapy. 1, 2

Appropriate indications for fluoroquinolones:

• Treatment failures after first-line antibiotics 1
• Complicated sinusitis involving frontal, ethmoidal, or sphenoidal sinuses (higher risk of serious complications) 3, 1
• Multi-drug resistant S. pneumoniae 1
• Severe beta-lactam allergy where cephalosporins are contraindicated 1

Levofloxacin is FDA-approved for acute bacterial sinusitis at 750 mg once daily for 5 days or 500 mg once daily for 10-14 days. 5 The 750 mg 5-day regimen showed 91.4% clinical success in microbiologically evaluable patients. 5

Adjunctive Therapies

Intranasal corticosteroids are recommended as adjuncts to antibiotic therapy in acute and chronic sinusitis. 1, 2

Additional supportive measures include:

• Analgesics (acetaminophen, NSAIDs) for pain 1
• Saline nasal irrigation for symptomatic relief 2
• Adequate hydration 1
• Short-term oral corticosteroids (typically 5 days) may be reasonable for patients with marked mucosal edema or who fail to respond to initial treatment 1

Important caveat: Systemic corticosteroids should not be used as monotherapy—antibiotics remain necessary to treat the underlying bacterial infection. 1

Watchful Waiting Option

For adults with uncomplicated acute bacterial sinusitis, watchful waiting without antibiotics is an appropriate initial strategy when follow-up can be assured. 1 Start antibiotics if no improvement by 7 days or worsening at any time. 1

The number needed to treat with antibiotics is 3-5 for persistent symptoms, meaning most viral cases resolve spontaneously. 1

Critical Pitfalls to Avoid

• Do not use doxycycline as first-line therapy: It has a predicted bacteriologic failure rate of 20-25% due to limited activity against H. influenzae and should only be considered for penicillin-allergic patients when better alternatives are unavailable. 1
• Ensure adequate treatment duration: Minimum 5 days, typically 7-10 days to prevent relapse 1
• Complete the full course: Even after symptoms improve, to prevent relapse 1
• Avoid fluoroquinolone overuse: Reserve for treatment failures or complicated disease to prevent resistance 1, 2

Diagnostic Confirmation Before Treatment

Antibiotics should only be initiated when acute bacterial sinusitis is confirmed by one of three clinical patterns: 2, 6

1. Persistent symptoms: Nasal discharge or congestion lasting ≥10 days without improvement 6
2. Severe onset: High fever ≥39°C AND purulent nasal discharge for at least 3-4 consecutive days 6
3. "Double sickening": Initial viral URI symptoms improve, then worsen with new fever, headache, or increased nasal discharge 6

Most acute rhinosinusitis cases are viral and resolve without antibiotics within 7 days. 1