First-Line Antibiotic for Acute Bacterial Sinusitis
Amoxicillin is the first-line antibiotic for acute bacterial sinusitis in adults, dosed at 500 mg twice daily for mild disease or 875 mg twice daily for moderate disease, for 5-10 days. 1, 2
Treatment Algorithm Based on Risk Factors
For Low-Risk Patients (No Recent Antibiotic Use, Mild Disease)
- Amoxicillin 500 mg twice daily for 10 days is the preferred first-line choice due to its safety, efficacy, low cost, and narrow microbiologic spectrum 1, 2
- This covers the three main pathogens: Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis 2, 3
- Shorter courses of 5-7 days have comparable efficacy with fewer side effects 1
For High-Risk Patients (Upgrade to Amoxicillin-Clavulanate)
Use amoxicillin-clavulanate 875 mg/125 mg twice daily if the patient has any of these risk factors 1:
- Antibiotic use in the past 4-6 weeks
- Age >65 years or <2 years
- Daycare attendance or close contact with children in daycare
- Moderate to severe symptoms
- Immunocompromised state
- Diabetes or chronic cardiac/hepatic/renal disease
- High local prevalence of resistant bacteria
- Frontal or sphenoidal sinusitis (more serious locations)
The clavulanate component provides coverage against β-lactamase-producing H. influenzae and M. catarrhalis, which account for 10-42% and nearly 100% of these organisms, respectively 2, 3
For Penicillin-Allergic Patients
Non-Severe Allergy (Rash, Mild Reactions)
Second- or third-generation cephalosporins are safe and effective 1, 4:
- Cefuroxime-axetil (second-generation) 1, 4
- Cefpodoxime-proxetil (third-generation, superior activity against H. influenzae) 1, 4
- Cefdinir (third-generation) 1, 4
The risk of cross-reactivity between penicillins and second/third-generation cephalosporins is negligible 4
Severe Type I Hypersensitivity (Anaphylaxis)
Reserve respiratory fluoroquinolones for true severe allergy 4:
What NOT to Use as First-Line
Avoid these antibiotics due to high resistance rates 1, 4:
- Azithromycin and macrolides: 20-25% resistance rates for S. pneumoniae and H. influenzae 1, 4
- Trimethoprim-sulfamethoxazole: 50% resistance for S. pneumoniae, 27% for H. influenzae 4
- Doxycycline: 20-25% bacteriologic failure rate, limited activity against H. influenzae 4
Treatment Duration
- Standard duration: 5-10 days until symptom-free for 7 days 1, 4, 2
- Some cephalosporins (cefuroxime-axetil, cefpodoxime-proxetil) are effective in 5-day courses 1
- Complete the full course even after symptoms improve to prevent relapse 4
When to Switch Antibiotics (Treatment Failure Protocol)
- If no improvement or worsening, switch to:
Watchful Waiting Option
For uncomplicated cases, consider delaying antibiotics for up to 7 days 1:
- Give the patient a prescription but instruct them to fill it only if symptoms don't improve after 7 days or worsen at any time
- This approach reduces antibiotic exposure and side effects while maintaining safety 1
Adjunctive Therapies to Improve Outcomes
- Intranasal corticosteroids (mometasone, fluticasone, budesonide twice daily) reduce mucosal inflammation and improve symptom resolution 4
- Analgesics (acetaminophen, NSAIDs) for pain relief 4
- Saline nasal irrigation for symptomatic relief 4
- Oral corticosteroids (short-term, 5 days) may be reasonable for marked mucosal edema or severe pain, but only as adjunctive therapy with antibiotics 4
Critical Pitfalls to Avoid
- Don't prescribe antibiotics for viral rhinosinusitis lasting <10 days unless severe symptoms are present 4
- Don't use fluoroquinolones as routine first-line therapy—reserve them for treatment failures or severe penicillin allergy to prevent resistance 1, 4
- Don't rely on mucus color alone to determine bacterial infection—color reflects neutrophils, not bacteria 4
- Don't continue ineffective therapy beyond 3-5 days—reassess and switch antibiotics 1, 4