First-Line Antibiotic for Acute Bacterial Sinusitis
Amoxicillin-clavulanate 875 mg/125 mg twice daily for 7-10 days is the preferred first-line antibiotic for acute bacterial sinusitis in adults, providing superior coverage against β-lactamase-producing organisms like H. influenzae and M. catarrhalis that have become increasingly prevalent. 1, 2, 3
Confirm Bacterial Sinusitis Before Prescribing Antibiotics
Before initiating any antibiotic, confirm the diagnosis meets one of three criteria:
- Persistent symptoms ≥10 days without improvement (nasal congestion, purulent discharge, facial pain) 1, 2
- Severe symptoms for ≥3 consecutive days (fever ≥39°C with purulent nasal discharge and facial pain) 1, 2
- "Double sickening": worsening symptoms after initial improvement from a viral upper respiratory infection 1, 2
Most acute rhinosinusitis (98-99.5%) is viral and resolves spontaneously within 7-10 days without antibiotics. 1, 2 Prescribing antibiotics before 10 days (unless severe symptoms are present) contributes to unnecessary adverse effects and antimicrobial resistance. 2
First-Line Treatment Options
For Patients Without Recent Antibiotic Use (Past 4-6 Weeks)
Amoxicillin-clavulanate 875 mg/125 mg twice daily is the preferred first-line choice due to increasing prevalence of β-lactamase-producing organisms. 1, 2, 3 This provides 90-91% predicted clinical efficacy and 97-99% bacteriologic efficacy. 1
Plain amoxicillin remains acceptable for uncomplicated cases:
- 500 mg twice daily for mild disease 1, 2
- 875 mg twice daily for moderate disease 1, 2
- Provides 87-88% clinical efficacy and 91-92% bacteriologic efficacy 1
The clavulanate component is critical because it provides coverage against β-lactamase-producing H. influenzae and M. catarrhalis, which have become increasingly prevalent. 2, 3
Treatment Duration
Treat for 7-10 days or until symptom-free for 7 days. 1, 2, 3 Shorter 5-7 day courses have comparable efficacy with fewer side effects. 2, 3
For Patients With Recent Antibiotic Use (Past 4-6 Weeks) or Moderate Disease
Prior antibiotic therapy within 4-6 weeks is a risk factor for infection with resistant organisms. 1
High-dose amoxicillin-clavulanate (4 g amoxicillin/250 mg clavulanate per day) provides enhanced coverage against drug-resistant S. pneumoniae (DRSP). 1 This achieves 91% clinical efficacy and 99% bacteriologic efficacy. 1
Respiratory fluoroquinolones (levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily for 10 days) are alternative first-line options for this population, providing 92% clinical efficacy and 100% bacteriologic efficacy. 1, 2
For Penicillin-Allergic Patients
Non-Type I Hypersensitivity (Rash, Mild Reactions)
Second- or third-generation cephalosporins are safe and preferred:
- Cefuroxime axetil (second-generation): 85% clinical efficacy, 87% bacteriologic efficacy 1, 2
- Cefpodoxime proxetil (third-generation): 87% clinical efficacy, 91% bacteriologic efficacy 1, 2
- Cefdinir (third-generation): 83% clinical efficacy, 85% bacteriologic efficacy 1, 2
Recent evidence shows the risk of serious allergic reactions to second- and third-generation cephalosporins in penicillin-allergic patients is negligible. 2
Type I Hypersensitivity (Anaphylaxis)
Respiratory fluoroquinolones are the treatment of choice:
These provide 92% clinical efficacy and 100% bacteriologic efficacy against both drug-resistant S. pneumoniae and β-lactamase-producing H. influenzae. 1, 2
What NOT to Use in Penicillin-Allergic Patients
Avoid TMP-SMX, doxycycline, and macrolides (azithromycin, clarithromycin, erythromycin) as first-line therapy. 1, 2 These have limited effectiveness against major pathogens of acute bacterial sinusitis, with bacterial failure rates of 20-25%. 1 Azithromycin should specifically not be used due to resistance patterns, with S. pneumoniae and H. influenzae resistance exceeding 20-25%. 2, 4
Pediatric Dosing (Age ≥6 Months)
High-dose amoxicillin-clavulanate 90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses is recommended for children with risk factors (age <2 years, daycare attendance, recent antibiotic use). 1, 2
Standard-dose amoxicillin 45 mg/kg/day in 2 divided doses is appropriate for mild disease without recent antibiotic use. 1, 2
For penicillin-allergic children, cefpodoxime proxetil 8 mg/kg/day in two doses is recommended. 2
Treatment Failure Protocol
Reassess at 72 hours (pediatrics) or 3-5 days (adults). 1, 2, 3 If no improvement or worsening symptoms:
Switch to:
- High-dose amoxicillin-clavulanate (4 g/250 mg per day) if not already used 1, 2
- Respiratory fluoroquinolones (levofloxacin 500-750 mg daily or moxifloxacin 400 mg daily) 1, 2
- Ceftriaxone 1-2 g IM/IV once daily for 5 days for patients unable to tolerate oral medications 1, 2
Adjunctive Therapies
Intranasal corticosteroids (mometasone, fluticasone, or budesonide twice daily) are strongly recommended as adjuncts to antibiotic therapy, as they reduce mucosal inflammation and improve symptom resolution. 2, 3
Short-term oral corticosteroids may be reasonable for patients with marked mucosal edema or acute hyperalgic sinusitis (severe pain) who fail to respond to initial treatment. 1, 2
Analgesics (acetaminophen, NSAIDs), saline nasal irrigation, and decongestants provide symptomatic relief. 1, 2
Critical Pitfalls to Avoid
Do not prescribe antibiotics for viral rhinosinusitis lasting <10 days unless severe symptoms are present—this contributes to antimicrobial resistance without clinical benefit. 1, 2
Do not use mucus color alone to determine antibiotic need—purulent discharge reflects neutrophils, not necessarily bacteria. 2
Reserve fluoroquinolones appropriately—avoid overuse in patients without allergies or treatment failures to prevent resistance development. 1, 2
Complete the full course of antibiotics even after symptoms improve to prevent relapse. 2
Never use clindamycin as monotherapy for sinusitis—it lacks activity against H. influenzae and M. catarrhalis and will fail in 30-40% of cases. 2
When to Refer to a Specialist
Refer to otolaryngology if: