What is the best antibiotic for acute bacterial sinusitis?

Best Antibiotic for Acute Bacterial Sinusitis

Amoxicillin remains the first-line antibiotic of choice for uncomplicated acute bacterial sinusitis in situations where antimicrobial resistance is not suspected. 1

First-Line Treatment Algorithm

For Uncomplicated Acute Bacterial Sinusitis:

• Standard-dose amoxicillin: 45 mg/kg/day in 2 divided doses for children ≥2 years; equivalent adult dosing 1
• Duration: 5-7 days (shorter course) to 10 days (traditional course) 1

When to Use High-Dose Amoxicillin (80-90 mg/kg/day in 2 divided doses):

• Communities with high prevalence (>10%) of nonsusceptible S. pneumoniae 1
• Severe infection (temperature ≥39°C/102°F) 1
• Risk of suppurative complications 1

When to Use Amoxicillin-Clavulanate Instead:

• Moderate to severe illness 1
• Children <2 years of age 1
• Child care attendance 1
• Recent antimicrobial use (within past 4 weeks) 1
• Healthcare environment exposure 1
• Failed prior antibiotic therapy 1
• Frontal or sphenoidal sinusitis 1
• Immunocompromised patients 1
• Adults >65 years 1

Alternative Antibiotics for Penicillin-Allergic Patients:

• Non-severe allergy: Second or third-generation cephalosporins (cefuroxime axetil, cefpodoxime proxetil) 1
• Severe allergy: Doxycycline or respiratory fluoroquinolones (levofloxacin, moxifloxacin) for adults 1
• Children with severe allergy: Clarithromycin or azithromycin 2

Treatment Failure Protocol:

• Assess for treatment failure if no improvement within 72 hours 1
• For partial response: Continue antibiotic for another 10-14 days 1
• For poor response: Switch to high-dose amoxicillin-clavulanate, cefuroxime, cefpodoxime, or cefprozil 1
• Consider parenteral therapy with ceftriaxone (50 mg/kg) for children who are vomiting or unable to tolerate oral medication 1

Important Clinical Considerations:

Bacterial Pathogens:

• Main pathogens: S. pneumoniae (30%), H. influenzae (30%), M. catarrhalis (10%) 1, 3
• Nearly 100% of M. catarrhalis and 10-42% of H. influenzae produce β-lactamase 1
• 10-15% of S. pneumoniae isolates are nonsusceptible to penicillin nationally, but can be as high as 50-60% in some areas 1

Treatment Duration:

• Shorter courses (5-7 days) may be equally effective as traditional 10-day courses 1
• Some experts recommend continuing treatment until the patient is symptom-free plus an additional 7 days 1

Common Pitfalls to Avoid:

1. Treating viral upper respiratory infections with antibiotics - ensure diagnosis of bacterial sinusitis is established 4
2. Using fluoroquinolones as first-line therapy - reserve these for treatment failures or high-risk situations 1
3. Inadequate dosing - use high-dose amoxicillin in areas with high resistance 1
4. Not considering local resistance patterns - familiarize yourself with local susceptibility data 1
5. Not reassessing after 72 hours - treatment failure requires prompt intervention 1

The recommendation for amoxicillin as first-line therapy is based on its effectiveness, safety, acceptable taste, low cost, and relatively narrow microbiologic spectrum 1. While some guidelines suggest amoxicillin-clavulanate as initial therapy due to increasing prevalence of β-lactamase-producing H. influenzae, the American Academy of Pediatrics guideline allows either amoxicillin or amoxicillin-clavulanate as first-line therapy based on risk factors 1.