What is the first line treatment for a patient with 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, though watchful waiting without immediate antibiotics is an equally appropriate initial strategy when reliable follow-up can be assured. 1, 2, 3

When to Prescribe Antibiotics vs. Watchful Waiting

Before prescribing any antibiotic, confirm the diagnosis meets one of three specific criteria 1, 2:

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

Watchful waiting is appropriate for all patients with uncomplicated acute bacterial sinusitis when follow-up is assured, with antibiotics started only if no improvement occurs by 7 days or symptoms worsen at any time. 1, 2 This approach is justified because 73-90% of patients improve spontaneously within 7-15 days without antibiotics, and the number needed to treat is 10-15 to get one additional person better. 1

First-Line Antibiotic Selection

Standard First-Line: Amoxicillin-Clavulanate

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is preferred over plain amoxicillin due to increasing prevalence of β-lactamase-producing organisms (Haemophilus influenzae and Moraxella catarrhalis). 1, 2, 3

Plain amoxicillin 500 mg twice daily (mild disease) or 875 mg twice daily (moderate disease) remains acceptable for uncomplicated cases without recent antibiotic exposure within the past 4-6 weeks. 1, 2

High-Dose Regimen for High-Risk Patients

Use high-dose amoxicillin-clavulanate (2 g amoxicillin/125 mg clavulanate twice daily) for patients with: 2, 3

• Recent antibiotic use within past month
• Age >65 years
• Moderate-to-severe symptoms
• Comorbid conditions (diabetes, COPD, immunosuppression)

Treatment Duration

Treat for 5-10 days, with most guidelines recommending treatment until symptom-free for 7 days (typically 10-14 days total). 1, 2, 3 Shorter 5-7 day courses have comparable efficacy with fewer adverse effects for uncomplicated cases. 1, 4

Penicillin-Allergic Patients

For documented penicillin allergy, the approach depends on allergy type 1, 2:

Non-severe allergy (rash, delayed reaction):

• Second-generation cephalosporins: Cefuroxime-axetil
• Third-generation cephalosporins: Cefpodoxime-proxetil, cefdinir, or cefprozil
• Cross-reactivity risk with cephalosporins is negligible for non-Type I allergies 2

Severe Type I allergy (anaphylaxis):

• Respiratory fluoroquinolones: Levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily for 10 days 1, 2, 5
• Doxycycline 100 mg once daily for 10 days is acceptable but has 20-25% predicted bacteriologic failure rate 2, 6

What NOT to Use as First-Line

Avoid these antibiotics due to high resistance rates: 1, 2

• Azithromycin and macrolides: 20-25% resistance for S. pneumoniae and H. influenzae 1, 2, 7
• Trimethoprim-sulfamethoxazole: 50% resistance for S. pneumoniae 2
• First-generation cephalosporins (cephalexin): Inadequate coverage against H. influenzae 2

When to Switch Antibiotics (Treatment Failure)

Reassess at 3-5 days: If no improvement, switch to high-dose amoxicillin-clavulanate or a respiratory fluoroquinolone. 1, 2, 3

Reassess at 7 days: If symptoms persist or worsen, reconfirm diagnosis and consider: 1, 2

• Levofloxacin 500-750 mg once daily for 10-14 days (90-92% predicted efficacy against resistant organisms) 2, 5
• Moxifloxacin 400 mg once daily for 10 days 2

Essential Adjunctive Therapies

These should be offered to ALL patients regardless of antibiotic choice 1, 2:

• Intranasal corticosteroids (mometasone, fluticasone, or budesonide twice daily) - reduces mucosal inflammation
• Saline nasal irrigation - removes mucus and provides symptomatic relief
• Analgesics (acetaminophen or ibuprofen) - relieves pain and fever
• Decongestants - may help breathing (topical use limited to ≤3 days to avoid rebound congestion)

Critical Pitfalls to Avoid

• Do not prescribe antibiotics for symptoms <10 days unless severe symptoms are present (fever ≥39°C with purulent discharge for ≥3 consecutive days) 1, 2, 6
• Do not use fluoroquinolones as routine first-line therapy in patients without β-lactam allergies - reserve for treatment failures to prevent resistance 1, 2
• Ensure adequate treatment duration (minimum 5 days, typically 7-10 days) to prevent relapse 1, 2, 3
• Do not use antihistamines or oral steroids routinely - they have side effects without proven benefit in acute bacterial sinusitis 1

Pediatric Dosing

For children with acute bacterial sinusitis 2:

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