What is the recommended antibiotic treatment for acute sinusitis?

Antibiotic Treatment for Acute Sinusitis

First-Line Treatment: Amoxicillin or Amoxicillin-Clavulanate

For most adults with acute bacterial sinusitis, start with amoxicillin 500 mg twice daily for uncomplicated cases or 875 mg twice daily for moderate disease, treating for 5-10 days. 1, 2

The choice between plain amoxicillin versus amoxicillin-clavulanate depends on disease severity and recent antibiotic exposure:

• Amoxicillin alone (500-875 mg twice daily) is appropriate for uncomplicated maxillary sinusitis without recent antibiotic use 1, 2
• Amoxicillin-clavulanate (875/125 mg twice daily) provides broader coverage against β-lactamase-producing organisms (Haemophilus influenzae, Moraxella catarrhalis) and should be used when initial amoxicillin fails or in areas with high resistance 1, 2

The evidence for high-dose amoxicillin-clavulanate (double amoxicillin component) is mixed. Two recent randomized trials found no significant benefit of high-dose over standard-dose formulations for clinically diagnosed acute sinusitis, though one trial using immediate-release formulation showed faster improvement at day 3 (52.4% vs 34.4%) but with increased severe diarrhea (15.8% vs 4.8%) 3, 4

Treatment Duration

• Standard duration is 5-10 days for uncomplicated acute bacterial sinusitis 1, 2, 5
• Some guidelines recommend treating until symptom-free for 7 days, typically totaling 10-14 days 1
• Shorter 5-day courses have demonstrated equivalent efficacy to 10-day regimens in multiple trials for uncomplicated maxillary sinusitis 5

Penicillin-Allergic Patients

For documented penicillin allergy, use second- or third-generation cephalosporins as first-line alternatives:

• Second-generation: Cefuroxime 250-500 mg twice daily 1, 2
• Third-generation: Cefpodoxime 200-400 mg twice daily or cefdinir (standard dosing) 1, 2
• The risk of cross-reactivity between penicillins and second/third-generation cephalosporins is negligible for non-Type I allergic reactions 1

Critical pitfall: Azithromycin and other macrolides should NOT be used as first-line therapy due to resistance rates of 20-25% among S. pneumoniae and H. influenzae 1, 2

Second-Line Treatment for Treatment Failure

If no improvement occurs after 3-5 days of initial therapy, switch to:

• Respiratory fluoroquinolones: Levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily for 10 days 1, 2
• Levofloxacin demonstrates 90-92% predicted clinical efficacy and provides excellent coverage against multi-drug resistant S. pneumoniae (MDRSP) and β-lactamase-producing organisms 1, 6
• The FDA has approved both levofloxacin 750 mg daily for 5 days and 500 mg daily for 10-14 days for acute bacterial sinusitis, with comparable efficacy (91.4% vs 88.6% clinical success) 6

Reserve fluoroquinolones as second-line therapy to prevent resistance development—they should not be routine first-line agents 1, 2

Treatment Based on Anatomic Location

• Maxillary sinusitis: Use standard first-line antibiotics (amoxicillin or amoxicillin-clavulanate) 1, 2
• Frontal, ethmoidal, or sphenoidal sinusitis: Consider fluoroquinolones (levofloxacin or moxifloxacin) due to risk of serious complications like meningitis or orbital involvement 1, 2

Adjunctive Therapies

• Intranasal corticosteroids (mometasone, fluticasone, budesonide) twice daily are recommended as adjuncts to antibiotics, reducing mucosal inflammation and improving symptom resolution 1, 2
• Short-term oral corticosteroids (e.g., dexamethasone 4 mg for 5 days) may be added for acute hyperalgic sinusitis (severe pain) or marked mucosal edema, but NEVER as monotherapy—always combine with antibiotics 1, 2
• Analgesics (acetaminophen, NSAIDs) for pain relief 1
• Saline nasal irrigation for symptomatic relief 1

Pediatric Dosing

• Standard-dose amoxicillin: 45 mg/kg/day divided into 2 doses for uncomplicated disease 1, 7
• High-dose amoxicillin: 80-90 mg/kg/day divided into 2 doses for high-risk children (age <2 years, daycare attendance, recent antibiotic use, or areas with high S. pneumoniae resistance) 1, 7
• 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 1

Critical Pitfalls to Avoid

• Do NOT prescribe antibiotics for viral rhinosinusitis lasting <10 days without bacterial features—98-99.5% of acute rhinosinusitis is viral and resolves spontaneously 1
• Confirm bacterial infection by identifying one of three patterns: persistent symptoms ≥10 days without improvement, severe symptoms (fever ≥39°C with purulent discharge) for ≥3 consecutive days, or "double sickening" (worsening after initial improvement) 1, 7
• Reassess at 3-5 days: If no improvement, switch antibiotics or re-evaluate diagnosis 1, 2
• Avoid first-generation cephalosporins (cephalexin, cefadroxil)—they lack adequate coverage for H. influenzae 2
• Complete the full antibiotic course even after symptoms improve to prevent relapse 1

Special Considerations

• Doxycycline (100 mg once daily for 10 days) is an acceptable alternative for penicillin-allergic patients but has limited activity against H. influenzae with predicted bacteriologic failure rates of 20-25% 1
• Trimethoprim-sulfamethoxazole should NOT be used due to high resistance rates (50% for S. pneumoniae, 27% for H. influenzae) 1
• Clindamycin should NEVER be used as monotherapy—it lacks activity against H. influenzae and M. catarrhalis and will fail in 30-40% of cases 1