What are the recommended antibiotics for treating bacterial sinus infections?

Antibiotic Treatment for Bacterial Sinus Infections

Amoxicillin-clavulanate is the first-line antibiotic for acute bacterial sinusitis in adults and children, with standard dosing of 875 mg/125 mg twice daily for adults and 45 mg/kg/day in 2 divided doses for children, treating for 7-10 days. 1, 2

When to Start Antibiotics

Not all sinus infections require antibiotics. Antibiotics should be reserved for bacterial sinusitis, which presents with:

• Persistent symptoms lasting >10 days without improvement 3
• Severe symptoms with high fever (≥39°C/102°F) and purulent nasal discharge for 3-4 consecutive days 3
• Worsening symptoms after initial improvement (double-worsening pattern) 3
• Frontal, ethmoidal, or sphenoidal sinusitis (antibiotics definitely indicated) 4

For uncomplicated maxillary sinusitis with mild symptoms, symptomatic treatment alone is reasonable initially, with antibiotics added only if symptoms persist or worsen. 4

First-Line Antibiotic Choices

Standard First-Line Options

For adults with mild-to-moderate disease:

• Amoxicillin-clavulanate 875 mg/125 mg twice daily (preferred due to resistance patterns) 1, 2
• Alternative: Amoxicillin 500 mg twice daily (if resistance not suspected) 1, 2

For children:

• Amoxicillin 45 mg/kg/day in 2 divided doses (standard) 1
• High-dose amoxicillin 80-90 mg/kg/day or amoxicillin-clavulanate 80-90 mg/kg/day (amoxicillin component) in high-risk situations 1

High-Risk Situations Requiring High-Dose Therapy

Use high-dose amoxicillin or amoxicillin-clavulanate when:

• Age <2 years 1
• Daycare attendance 1
• Recent antibiotic use (within 4-6 weeks) 1
• Geographic areas with high prevalence of resistant S. pneumoniae (>10-15% nonsusceptible) 1

Important caveat: Recent research shows that high-dose amoxicillin-clavulanate (1750-2000 mg amoxicillin component) does not provide superior clinical outcomes compared to standard dosing in adults, but does increase severe diarrhea risk (15.8% vs 4.8%). 5, 6 Therefore, standard dosing is preferred for most adult patients.

Penicillin-Allergic Patients

For true penicillin allergy, use:

• Cefdinir 1, 2
• Cefuroxime 1, 2
• Cefpodoxime 1, 2

Critical pitfall: Azithromycin and other macrolides should NOT be used due to high resistance rates among S. pneumoniae and H. influenzae. 2 This is a common prescribing error that must be avoided.

Site-Specific Treatment Considerations

Maxillary Sinusitis (Most Common)

• First-line: Amoxicillin-clavulanate or cephalosporins as above 4
• Symptoms: Unilateral/bilateral infraorbital pain worsening when bending forward, pulsatile pain peaking in evening 4

Frontal, Ethmoidal, or Sphenoidal Sinusitis (High-Risk)

These require more aggressive therapy due to complication risk:

• Consider respiratory fluoroquinolones (levofloxacin 500-750 mg daily or moxifloxacin 400 mg daily) 4, 2
• These sites carry risk of serious complications including meningitis, orbital complications, and intracranial extension 4
• Red flags requiring immediate hospitalization: meningeal signs, exophthalmos, palpebral edema, ocular mobility disorders, pain preventing sleep 4

Treatment Duration

Standard duration: 7-10 days 4

Some experts recommend treating until symptom-free, then continuing for an additional 7 days (typically 10-14 days total). 2, 3 Shorter courses (5 days) with certain cephalosporins (cefuroxime-axetil, cefpodoxime-proxetil) have shown efficacy. 4

For levofloxacin, both 5-day (750 mg daily) and 10-14 day (500 mg daily) regimens are FDA-approved and equally effective. 7

Treatment Failure Protocol

If no improvement after 3-5 days of initial therapy:

1. Switch to broader-spectrum antibiotic 2
2. For initial amoxicillin failures: Switch to amoxicillin-clavulanate 2
3. For initial amoxicillin-clavulanate failures: Switch to respiratory fluoroquinolone (levofloxacin or moxifloxacin) 4, 2
4. Consider imaging (CT scan) to confirm diagnosis and assess for complications 2

Adjunctive Therapies

Intranasal corticosteroids are recommended as adjuncts to antibiotics in both acute and chronic sinusitis. 2

Short-term oral corticosteroids may be beneficial in acute hyperalgic sinusitis (severe pain) or marked mucosal edema, but should not be used as monotherapy. 2

Supportive measures: adequate hydration, analgesics, warm facial packs, sleeping with head elevated. 2

Key Microbiology and Resistance Patterns

The predominant pathogens are:

• Streptococcus pneumoniae (10-15% nonsusceptible to penicillin) 1
• Haemophilus influenzae (10-42% β-lactamase positive) 1
• Moraxella catarrhalis (nearly 100% β-lactamase positive) 1

This resistance pattern explains why amoxicillin-clavulanate is preferred over amoxicillin alone for empiric therapy. 1

Common Pitfalls to Avoid

1. Do not prescribe azithromycin or clarithromycin for sinusitis due to high resistance rates 2
2. Do not use fluoroquinolones as first-line therapy for uncomplicated maxillary sinusitis—reserve for complicated cases or treatment failures 4, 2
3. Do not prescribe antibiotics for viral rhinosinusitis (symptoms <10 days without worsening) 2
4. Do not assume high-dose amoxicillin-clavulanate is superior in adults—it increases side effects without improving outcomes 5, 6
5. Complete the full antibiotic course even after symptom improvement to prevent relapse 2