What are the recommended antibiotics for treating acute bacterial sinusitis?

Antibiotic Recommendations for Acute Bacterial Sinusitis

First-Line Treatment

Amoxicillin-clavulanate is the preferred first-line antibiotic for acute bacterial sinusitis in both adults and children, dosed at 875 mg/125 mg twice daily for adults (5-7 days) and 80-90 mg/kg/day of the amoxicillin component for children (10-14 days). 1, 2

The superiority of amoxicillin-clavulanate over plain amoxicillin is driven by the increasing prevalence of β-lactamase-producing Haemophilus influenzae (20-30% of cases) and Moraxella catarrhalis (12-28% of cases), which render plain amoxicillin ineffective. 2, 3 While older guidelines from 2004 listed plain amoxicillin as acceptable for mild disease without recent antibiotic exposure 4, the most recent evidence strongly favors amoxicillin-clavulanate as initial therapy due to these resistance patterns. 1, 2

Adult Dosing

• Standard dose: 875 mg/125 mg twice daily for 5-7 days 1, 2
• High-dose formulation: 2000 mg/125 mg twice daily may be considered for severe infections or areas with high drug-resistant S. pneumoniae (DRSP) prevalence 4, 1

However, recent high-quality randomized trials found no significant benefit of high-dose over standard-dose amoxicillin-clavulanate in adults with clinically diagnosed acute sinusitis. 5, 6 Therefore, standard dosing (875/125 mg twice daily) is recommended for most adults to minimize adverse effects, particularly severe diarrhea, which occurred in 15.8% of high-dose patients versus 4.8% of standard-dose patients. 6

Pediatric Dosing

• High-dose amoxicillin-clavulanate: 80-90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses for 10-14 days 1, 2
• This high-dose regimen is particularly important for children <2 years, those in daycare, or with recent antibiotic exposure 1, 2

Penicillin-Allergic Patients

For patients with documented penicillin allergy, second-generation cephalosporins (cefuroxime) or third-generation cephalosporins (cefpodoxime, cefdinir) are the preferred alternatives, as the risk of serious cross-reactivity is negligible. 1, 2

Recommended Alternatives

• Cefuroxime-axetil (second-generation): Effective for maxillary sinusitis 1
• Cefpodoxime-proxetil (third-generation): Superior activity against H. influenzae 1, 3
• Cefdinir (third-generation): Excellent coverage and convenient dosing 1, 3

Critical caveat: Azithromycin and other macrolides should NOT be used for acute bacterial sinusitis due to 20-25% resistance rates among S. pneumoniae and H. influenzae. 1, 7 Despite FDA approval for 3-day azithromycin therapy 7, multiple guidelines explicitly exclude macrolides from recommended therapy. 1

Second-Line Treatment for Failure

If no improvement occurs within 72 hours (pediatrics) or 3-5 days (adults), switch to a respiratory fluoroquinolone—specifically levofloxacin 500-750 mg once daily or moxifloxacin. 1, 2

Fluoroquinolones demonstrate 90-92% predicted clinical efficacy and 100% microbiologic eradication of S. pneumoniae, including multi-drug resistant strains (MDRSP). 1, 8 However, fluoroquinolones must be reserved for treatment failures or complicated sinusitis to prevent resistance development—they should never be routine first-line therapy. 4, 1

When to Use Fluoroquinolones

• Treatment failure after 3-5 days of first-line therapy 1, 2
• Frontal, ethmoidal, or sphenoidal sinusitis (higher complication risk) 1
• Multi-drug resistant S. pneumoniae documented or suspected 1, 8
• Severe beta-lactam allergy where cephalosporins are contraindicated 1

The FDA label confirms levofloxacin's efficacy for acute bacterial sinusitis with both 5-day (750 mg) and 10-14 day (500 mg) regimens, showing 91.4% and 88.6% clinical success rates respectively. 8

Treatment Duration

• Adults: 5-7 days is sufficient for uncomplicated cases 1, 2
• Children: 10-14 days remains standard 1, 2
• General principle: Treat until symptom-free for 7 days 4, 1

Shorter courses (5-7 days) have comparable efficacy with fewer side effects in adults. 2 A 5-day gatifloxacin course showed equivalent cure rates (74%) to 10-day amoxicillin-clavulanate (72%) in a randomized trial. 9

Adjunctive Therapies

Intranasal corticosteroids should be added to antibiotic therapy in all patients with acute bacterial sinusitis, particularly those with allergic rhinitis, to reduce inflammation and improve outcomes. 1, 2

Additional supportive measures include:

• Intranasal saline irrigation (physiologic or hypertonic) for adults 2
• Adequate hydration, analgesics, warm facial packs 1
• Short-term oral corticosteroids (e.g., dexamethasone 4 mg) for severe pain or marked mucosal edema 1

Important: Systemic corticosteroids should never be used as monotherapy—antibiotics remain essential for bacterial infection. 1

Critical Pitfalls to Avoid

1. Do not use plain amoxicillin as first-line therapy given high prevalence of β-lactamase-producing organisms 2

2. Do not prescribe antibiotics for viral rhinosinusitis—ensure patients meet diagnostic criteria: symptoms >10 days without improvement, severe symptoms with high fever and purulent discharge for 3-4 days, or worsening after initial improvement 4, 2

3. Do not continue ineffective antibiotics beyond 3-5 days—failure to reassess and switch therapy leads to prolonged illness and potential complications 1, 2

4. Do not use azithromycin or clarithromycin due to significant resistance patterns 1, 7

5. Do not routinely cover for MRSA during initial empiric therapy, as current data do not support this practice 2

6. Reassess at 72 hours (pediatrics) or 3-5 days (adults) if symptoms worsen or fail to improve 1, 2

When to Refer to Specialist

Refer to otolaryngologist, infectious disease specialist, or allergist for:

• Immunocompromised patients 2
• Clinical deterioration despite extended antibiotic courses 2
• Recurrent sinusitis (≥3 episodes per year) with clearing between episodes 1, 2
• Suspected complications (orbital or intracranial involvement) 2
• Sinusitis refractory to usual antibiotic treatment 1