What is the first-line antibiotic for acute bacterial sinusitis?

First-Line Antibiotic for Acute Bacterial Sinusitis

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is the preferred first-line antibiotic for acute bacterial sinusitis in adults. 1

When to Use Amoxicillin Alone vs. Amoxicillin-Clavulanate

Start with amoxicillin-clavulanate (not plain amoxicillin) if the patient has:

• Recent antibiotic use within the past 3 months 1
• Moderate to severe symptoms 1
• Age >65 years 1
• Diabetes or other chronic comorbidities 1
• Immunocompromised status 1
• High local prevalence of penicillin-resistant S. pneumoniae 1
• Close contact with daycare children 1
• Current smoking 1

Plain amoxicillin 1.5-4 g/day may be used only for:

• Mild disease without recent antibiotic exposure 1
• Patients without the risk factors listed above 1

The clavulanate component provides essential coverage against β-lactamase-producing H. influenzae and M. catarrhalis, which have become increasingly prevalent. 2 Given that most patients presenting with acute bacterial sinusitis have at least one risk factor, amoxicillin-clavulanate should be considered the default first-line choice. 1

Treatment Duration

Treat for 5-7 days in uncomplicated cases, which provides comparable efficacy to 10 days with fewer adverse effects. 1 However, use the standard 10-day duration for severe infection, immunocompromised patients, or frontal/sphenoidal sinusitis. 1

For Penicillin-Allergic Patients

If the patient has a documented penicillin allergy (non-anaphylactic rash or mild reaction):

• Use second-generation cephalosporins: cefuroxime-axetil 1, 2
• Or third-generation cephalosporins: cefpodoxime-proxetil or cefdinir 1, 2
• The risk of cross-reactivity between penicillins and second/third-generation cephalosporins is negligible in patients without anaphylaxis history 3

If the patient has a true Type I hypersensitivity (anaphylaxis) to penicillin:

• Use respiratory fluoroquinolones: levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily for 5-10 days 1, 4, 5
• Doxycycline 100 mg twice daily is an alternative but has lower efficacy (81% clinical success, 80% bacteriologic efficacy) 1

Critical Pitfalls to Avoid

Never use azithromycin or other macrolides as first-line therapy due to 20-25% resistance rates among S. pneumoniae and H. influenzae. 2

Reserve fluoroquinolones for specific situations only to prevent resistance development: 1, 2

• True penicillin anaphylaxis
• Treatment failure after 72 hours
• Complicated sinusitis (frontal, ethmoidal, or sphenoidal)
• Multi-drug resistant S. pneumoniae

Do not use first-generation cephalosporins (cephalexin, cefadroxil) as they have poor coverage for H. influenzae. 3

Avoid cefixime and ceftibuten due to poor activity against S. pneumoniae, especially penicillin-resistant strains. 3

When to Reassess and Switch Antibiotics

Reassess at 72 hours if symptoms fail to improve or worsen at any time. 1 Switch to:

• Respiratory fluoroquinolone (levofloxacin or moxifloxacin) 1
• High-dose amoxicillin-clavulanate (2000 mg amoxicillin component twice daily) 1
• Ceftriaxone 1 g IM/IV daily for 5 days 1

After 7 days without improvement, reevaluate for misdiagnosis, complications, or need for imaging/endoscopy. 1

Adjunctive Therapies

Add intranasal corticosteroids as they reduce symptoms and may decrease antibiotic duration. 2, 3

Consider short-term oral corticosteroids (typically 5 days) for patients with severe pain (acute hyperalgic sinusitis) or marked mucosal edema who fail initial treatment. 2

Provide supportive care: analgesics (acetaminophen, NSAIDs), saline nasal irrigation, adequate hydration, and short-term decongestants as needed. 2, 3

Watchful Waiting Option

For uncomplicated acute bacterial sinusitis with assured follow-up, watchful waiting without immediate antibiotics is appropriate, with antibiotics started if no improvement by 7 days or worsening at any time. 1 This approach reduces adverse events and antibiotic resistance. 1