What is the first line treatment for acute bacterial sinusitis?

First-Line Treatment for Acute Bacterial Sinusitis

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line antibiotic for acute bacterial sinusitis in adults, providing superior coverage against β-lactamase-producing organisms (Haemophilus influenzae and Moraxella catarrhalis) that have become increasingly prevalent. 1, 2

When to Prescribe Antibiotics (Not All "Sinusitis" Needs Antibiotics)

Before prescribing any antibiotic, confirm bacterial infection by identifying one of three specific patterns: 1, 3

• Persistent symptoms ≥10 days without improvement (nasal discharge, congestion, facial pain/pressure) 1, 3
• Severe symptoms for ≥3 consecutive days (fever ≥39°C with purulent nasal discharge) 1, 3
• "Double sickening" - worsening symptoms after initial improvement from a viral upper respiratory infection 1, 3

Critical pitfall: 98-99.5% of acute rhinosinusitis is viral and resolves spontaneously within 7-10 days without antibiotics—do not prescribe antibiotics for symptoms lasting <10 days unless severe symptoms are present. 1, 3

First-Line Antibiotic Selection

Standard First-Line: Amoxicillin-Clavulanate

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is now preferred over plain amoxicillin due to increasing prevalence of β-lactamase-producing H. influenzae (nearly 50% of strains) and M. catarrhalis (90-100% of strains). 1, 2, 4

Alternative First-Line: Plain Amoxicillin (Limited Use)

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 within the past 4-6 weeks. 1, 3

Why the shift to amoxicillin-clavulanate? The clavulanate component provides essential coverage against β-lactamase-producing organisms that render plain amoxicillin ineffective in 40-50% of cases. 1, 4

Treatment Duration

• Standard duration: 5-10 days, with most guidelines recommending treatment until symptom-free for 7 days (typically 10-14 days total) 1, 2, 3
• Shorter courses (5-7 days) have comparable efficacy with fewer side effects 3
• Reassess at 3-5 days: If no improvement, switch antibiotics or re-evaluate diagnosis 1, 2, 3

Penicillin-Allergic Patients

Non-Severe Allergy (Rash, Mild Reactions)

Second- or third-generation cephalosporins are safe and effective: 1, 2, 3

• Cefuroxime-axetil (second-generation) 1, 2
• Cefpodoxime-proxetil (third-generation, superior H. influenzae coverage) 1, 2
• Cefdinir (third-generation) 1, 2

Evidence note: Recent data show the risk of serious allergic reactions to second- and third-generation cephalosporins in penicillin-allergic patients is negligible. 1

Severe Type I Hypersensitivity (Anaphylaxis)

Respiratory fluoroquinolones are the appropriate choice: 1, 3

• Levofloxacin 500 mg once daily for 10-14 days 1, 5
• Moxifloxacin 400 mg once daily for 10 days 1

Second-Line Treatment for Failure

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

1. High-dose amoxicillin-clavulanate (if not already used): 2000 mg amoxicillin/125 mg clavulanate twice daily 1
2. Respiratory fluoroquinolones: Levofloxacin 500-750 mg once daily or moxifloxacin 400 mg once daily 1, 5
3. Third-generation cephalosporins: Cefpodoxime or cefdinir (superior H. influenzae activity) 1

Fluoroquinolone efficacy: Levofloxacin demonstrates 90-92% predicted clinical efficacy with 100% microbiologic eradication for S. pneumoniae, including multi-drug resistant strains. 1, 5

Adjunctive Therapies (Use in ALL Patients)

• Intranasal corticosteroids (mometasone, fluticasone, budesonide) twice daily - strong evidence for symptom improvement 1, 2, 3
• Analgesics (acetaminophen, NSAIDs) for pain and fever 1, 3
• Saline nasal irrigation for symptomatic relief 1, 3
• Short-term oral corticosteroids may be considered for marked mucosal edema or severe pain, but never without concurrent antibiotics 1, 2

Antibiotics to AVOID

• Azithromycin and macrolides: Explicitly contraindicated due to 20-25% resistance rates for S. pneumoniae and H. influenzae 1
• Trimethoprim-sulfamethoxazole: High resistance rates (50% for S. pneumoniae, 27% for H. influenzae) 1
• First-generation cephalosporins (cephalexin): Inadequate coverage against H. influenzae (nearly 50% β-lactamase producing) 1
• Clindamycin monotherapy: Lacks activity against H. influenzae and M. catarrhalis 1

Critical Pitfalls to Avoid

• Do not prescribe antibiotics for viral rhinosinusitis lasting <10 days unless severe symptoms are present 1, 3
• Reserve fluoroquinolones for treatment failures, severe penicillin allergy, or complicated sinusitis to prevent resistance development 1, 2, 3
• Ensure adequate treatment duration (minimum 5 days, typically 7-10 days) to prevent relapse 1, 2
• Reassess at 3-5 days if no improvement—do not continue ineffective therapy 1, 2, 3
• Never use systemic corticosteroids without antibiotics when bacterial sinusitis is suspected, as this may suppress immune response and allow bacterial proliferation 1

Pediatric Dosing Considerations

• 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 high local resistance rates) 1
• High-dose amoxicillin-clavulanate: 80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses 1

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 if no improvement by 7 days or worsening at any time. 1 The number needed to treat with antibiotics is 10-15 to get one additional person better after 7-15 days. 1