What is the first line treatment for sinusitis?

First-Line Treatment for Acute Bacterial Sinusitis

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 7-10 days is the preferred first-line antibiotic for acute bacterial sinusitis in adults, providing superior coverage against β-lactamase-producing organisms (H. influenzae and M. catarrhalis) that have become increasingly prevalent. 1, 2

When to Prescribe Antibiotics (Not All Sinusitis Needs Antibiotics)

Most acute rhinosinusitis (98-99.5%) is viral and resolves spontaneously within 7-10 days without antibiotics. 1 Only prescribe antibiotics when bacterial sinusitis is confirmed by one of three patterns: 1, 2

• Persistent symptoms ≥10 days without clinical improvement 1, 2
• Severe symptoms for ≥3 consecutive days: fever ≥39°C with purulent nasal discharge and facial pain 1, 2
• "Double sickening": worsening symptoms after initial improvement from a viral upper respiratory infection 1, 2

First-Line Antibiotic Selection

Standard First-Line: Amoxicillin-Clavulanate

• Amoxicillin-clavulanate 875 mg/125 mg twice daily is preferred over plain amoxicillin due to increasing prevalence of β-lactamase-producing organisms (nearly 50% of H. influenzae and 90-100% of M. catarrhalis). 1, 2
• Plain amoxicillin 500 mg twice daily (mild disease) or 875 mg twice daily (moderate disease) remains acceptable only for uncomplicated cases without recent antibiotic exposure. 1, 2

Treatment Duration

• 7-10 days is the standard duration, with treatment continuing until symptom-free for 7 days (typically 10-14 days total). 1, 2
• Some second- and third-generation cephalosporins are effective in 5-day courses. 1, 2

Penicillin-Allergic Patients

For documented penicillin allergy (non-anaphylactic reactions), second- or third-generation cephalosporins are safe and effective: 1, 2

• Second-generation: Cefuroxime-axetil 1, 2
• Third-generation: Cefpodoxime-proxetil, cefdinir, or cefprozil 1, 2

The risk of cross-reactivity between penicillins and second/third-generation cephalosporins is negligible for non-severe allergies. 1

For severe penicillin allergy (anaphylaxis), use respiratory fluoroquinolones: 1

• Levofloxacin 500 mg once daily for 10-14 days 1
• Moxifloxacin 400 mg once daily for 10 days 1

Critical caveat: Never use azithromycin or other macrolides as first-line therapy—resistance rates exceed 20-25% for both S. pneumoniae and H. influenzae. 1

Adjunctive Therapies (Use Alongside Antibiotics)

• Intranasal corticosteroids (mometasone, fluticasone, budesonide) twice daily reduce mucosal inflammation and improve symptom resolution. 1, 3
• Analgesics (acetaminophen or NSAIDs) for pain and fever relief. 1, 3
• Saline nasal irrigation provides symptomatic relief and promotes drainage. 1, 3
• Oral decongestants (pseudoephedrine) for symptomatic relief, but topical decongestants should not exceed 3 days due to risk of rhinitis medicamentosa. 1, 3

Treatment Failure Protocol

If no improvement after 3-5 days of initial therapy: 1, 2

• Switch to high-dose amoxicillin-clavulanate (2000 mg/125 mg twice daily or 90 mg/kg/day in children) 1
• Alternative: Respiratory fluoroquinolones (levofloxacin 500-750 mg once daily or moxifloxacin 400 mg once daily) 1, 2
• Consider third-generation cephalosporins (cefpodoxime, cefdinir) for superior H. influenzae coverage 1

Pediatric Dosing

• Standard-dose amoxicillin: 45 mg/kg/day in 2 divided doses 1
• High-dose amoxicillin: 80-90 mg/kg/day in 2 divided doses for high-risk children (age <2 years, daycare attendance, recent antibiotic use, or areas with high S. pneumoniae resistance) 1
• Amoxicillin-clavulanate: 80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses 1

Critical Pitfalls to Avoid

• Do not prescribe antibiotics for symptoms lasting <10 days unless severe symptoms are present—this contributes to antimicrobial resistance without clinical benefit. 1, 3
• Never use first-generation cephalosporins (cephalexin) for sinusitis—they have inadequate coverage against H. influenzae. 1
• Avoid fluoroquinolones as routine first-line therapy—reserve them for treatment failures, severe penicillin allergy, or complicated sinusitis to prevent resistance development. 1, 2
• Complete the full antibiotic course even after symptoms improve to prevent relapse. 1
• Reassess at 3-5 days: If no improvement, switch antibiotics or re-evaluate the diagnosis. 1, 2

Watchful Waiting Option

For adults with uncomplicated acute bacterial sinusitis, watchful waiting without immediate antibiotics is appropriate when follow-up can be assured, with antibiotics started only 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. 1