First-Line Treatment for Acute Bacterial Sinusitis (No Penicillin Allergy)
Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line antibiotic for acute bacterial sinusitis in adults without penicillin allergy. 1
Confirming Bacterial Sinusitis Before Starting Antibiotics
Before prescribing antibiotics, confirm the diagnosis meets one of three bacterial criteria 1:
- Persistent symptoms ≥10 days without improvement (nasal discharge, congestion, facial pain/pressure) 1
- Severe symptoms ≥3 consecutive days: fever ≥39°C with purulent nasal discharge 1
- "Double sickening": worsening after initial improvement from a viral upper respiratory infection 1
Most acute rhinosinusitis (98-99.5%) is viral and resolves spontaneously within 7-10 days without antibiotics 1. Do not prescribe antibiotics for symptoms lasting <10 days unless severe symptoms are present 1.
First-Line Antibiotic Choice and Dosing
Standard-dose amoxicillin-clavulanate 875 mg/125 mg twice daily is the preferred first-line agent because it provides coverage against β-lactamase-producing Haemophilus influenzae and Moraxella catarrhalis, which have become increasingly prevalent 1.
High-dose amoxicillin-clavulanate (2 g/125 mg twice daily) should be used for patients with 1:
- Recent antibiotic use within the past month
- Age >65 years
- Moderate-to-severe symptoms
- Comorbid conditions
- Immunocompromised state
Plain amoxicillin 500 mg twice daily (mild disease) or 875 mg twice daily (moderate disease) remains acceptable for uncomplicated cases without recent antibiotic exposure 1.
Treatment Duration
Treat for 5-10 days, with most guidelines recommending treatment until symptom-free for 7 days (typically 10-14 days total) 1. Shorter 5-7 day courses have comparable efficacy with fewer side effects 1.
Essential Adjunctive Therapies
Add these to improve outcomes regardless of antibiotic choice 1:
- Intranasal corticosteroids (mometasone, fluticasone, or budesonide twice daily): reduce mucosal inflammation and improve symptom resolution 1
- Saline nasal irrigation: provides symptomatic relief and promotes drainage 1
- Analgesics (acetaminophen or NSAIDs): manage pain and fever 1
- Adequate hydration: helps thin secretions 1
When to Reassess and Switch Antibiotics
Reassess at 3-5 days 1:
- If no improvement, switch to high-dose amoxicillin-clavulanate, a respiratory fluoroquinolone (levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily), or a third-generation cephalosporin 1
Reassess at 7 days 1:
- If symptoms persist or worsen, reconfirm diagnosis and consider complications (orbital cellulitis, meningitis) 1
- Switch to broader-spectrum antibiotics if bacterial sinusitis is confirmed 1
Watchful Waiting Option
For adults with uncomplicated acute bacterial sinusitis, watchful waiting without immediate antibiotics is an appropriate initial strategy when reliable follow-up can be assured 1. Start antibiotics only if no improvement by 7 days or symptoms worsen at any time 1.
Critical Pitfalls to Avoid
- Do not use azithromycin or other macrolides as first-line therapy due to 20-25% resistance rates 1
- Do not use first-generation cephalosporins (cephalexin, cefadroxil) due to inadequate coverage against H. influenzae 1
- Do not use fluoroquinolones as first-line therapy in patients without documented β-lactam allergies to avoid promoting antimicrobial resistance 1
- Do not prescribe antibiotics for viral rhinosinusitis lasting <10 days unless severe symptoms are present 1
- Ensure adequate treatment duration (minimum 5 days, typically 7-10 days) to prevent relapse 1
Expected Timeline for Improvement
Most patients should experience noticeable improvement within 3-5 days of starting appropriate antibiotic therapy 1. By 7 days, approximately 73-85% of patients show clinical improvement 1. Complete resolution typically occurs by 10-14 days or when symptom-free for 7 consecutive days 1.