Recommended Antibiotic for Bacterial Sinus Infections
Amoxicillin 500 mg twice daily for 10-14 days is the first-line antibiotic for most adults with acute bacterial sinusitis. 1, 2
First-Line Treatment Algorithm
Standard-Risk Patients:
- Amoxicillin 500 mg twice daily is the preferred initial choice for uncomplicated acute bacterial sinusitis 1, 2
- Treatment duration: 10-14 days until symptom-free for 7 days 1
- This recommendation is based on predicted effectiveness against the most common pathogens: Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis 3, 2
High-Risk Patients (requiring higher doses):
Consider high-dose amoxicillin (875 mg twice daily) or amoxicillin-clavulanate (875/125 mg twice daily) for: 1, 2
- Age <2 years or >65 years
- Recent antibiotic use within 4-6 weeks
- Daycare attendance
- Geographic areas with high prevalence of resistant S. pneumoniae (>25% resistance)
- Severe infection presentation 1
Important caveat: Recent high-quality evidence from 2021 found that high-dose amoxicillin-clavulanate did NOT provide superior outcomes compared to standard dosing in adults, though it did increase severe diarrhea rates (7.7% vs 7.0%) 4. However, a 2018 study showed conflicting results with immediate-release formulations 5. Given this equipoise and guideline recommendations, standard dosing remains appropriate for most patients.
Penicillin-Allergic Patients
For true penicillin allergy, use second or third-generation cephalosporins: 1, 2
- Cefuroxime 250-500 mg twice daily
- Cefpodoxime 200-400 mg twice daily
- Cefdinir (third-generation option)
Critical pitfall to avoid: Do NOT use azithromycin or other macrolides for acute bacterial sinusitis due to significant resistance patterns among S. pneumoniae and H. influenzae 1. Multiple guidelines explicitly exclude macrolides from recommended therapy.
Second-Line Treatment (Treatment Failure)
If no improvement after 3-5 days of initial therapy: 1
Switch to amoxicillin-clavulanate 875/125 mg twice daily for better coverage against β-lactamase-producing organisms 1. Nearly 50% of H. influenzae and 90-100% of M. catarrhalis produce β-lactamase 3.
Location-Based Treatment Considerations
Maxillary sinusitis (most common):
- Use standard first-line antibiotics as above 1
- Clinical clues: unilateral/bilateral infraorbital pain worsening when bending forward, pulsatile quality, peaks evening/night 1
Frontal, ethmoidal, or sphenoidal sinusitis:
- Consider respiratory fluoroquinolones due to risk of serious complications: 1, 6
- Fluoroquinolones provide 90-92% predicted clinical efficacy and 100% microbiologic eradication of S. pneumoniae 1
Critical caveat: Reserve fluoroquinolones as second-line therapy to prevent resistance development 1. They should NOT be routine first-line treatment for uncomplicated maxillary sinusitis.
Pediatric Dosing
Standard therapy: 1
- Amoxicillin 45 mg/kg/day in 2 divided doses
High-risk pediatric patients: 1
- Amoxicillin-clavulanate 80-90 mg/kg/day (amoxicillin component) with 6.4 mg/kg/day clavulanate in 2 divided doses
Penicillin-allergic children: 1
- Cefpodoxime proxetil 8 mg/kg/day in 2 doses
Adjunctive Therapy
Intranasal corticosteroids are recommended as adjunct to antibiotics in both acute and chronic sinusitis 1. Short-term oral corticosteroids may be reasonable for marked mucosal edema or treatment failure 1.
Common Pitfalls to Avoid
- Do NOT prescribe antibiotics for viral upper respiratory infections - this is strongly discouraged 3
- Do NOT use first-generation cephalosporins (cephalexin, cefadroxil) - they have poor coverage for H. influenzae 3
- Do NOT use cefaclor - inadequate activity against β-lactamase-producing organisms and high risk of serum sickness-like reactions 3
- Do NOT use azithromycin - resistance patterns make it unsuitable 1
- Complete the full antibiotic course even after symptom improvement to prevent relapse 1