What is the recommended treatment for acute bacterial sinusitis?

Treatment of Acute Bacterial Sinusitis

For acute bacterial sinusitis, initiate amoxicillin-clavulanate as first-line empiric therapy rather than amoxicillin alone, with high-dose formulations (amoxicillin 2g twice daily or 90 mg/kg/day in children) reserved for patients with risk factors for resistant pathogens. 1, 2

Diagnosis Before Treatment

Confirm acute bacterial sinusitis using one of three clinical presentations before prescribing antibiotics 1:

• Persistent symptoms lasting ≥10 days without improvement (nasal discharge, congestion, facial pain/pressure, or cough) 1
• Severe onset with high fever (≥39°C) and purulent nasal discharge for at least 3-4 consecutive days at illness onset 1
• "Double-sickening" pattern: worsening symptoms after initial improvement from a typical viral URI lasting 5-6 days 1

First-Line Antibiotic Selection

Standard Dosing (Most Patients)

Amoxicillin-clavulanate is preferred over amoxicillin alone for both adults and children 1, 2:

• Adults: Amoxicillin 875 mg/clavulanate 125 mg twice daily 1
• Children: Amoxicillin 45 mg/kg/day divided twice daily (based on amoxicillin component) 1

The IDSA guideline strongly recommends amoxicillin-clavulanate over amoxicillin alone in children (strong, moderate evidence) and weakly recommends it in adults (weak, low evidence) 1. This preference is based on increasing prevalence of β-lactamase-producing H. influenzae and M. catarrhalis, which account for nearly 50% and 90-100% of isolates respectively 1.

High-Dose Formulations (Risk Factors Present)

Use high-dose amoxicillin-clavulanate when patients have 1, 2:

• Age <2 years or >65 years 1
• Daycare attendance 1
• Recent antibiotic use (within past 4-6 weeks) 1, 2
• Recent hospitalization (past 5 days) 1
• Geographic areas with high penicillin-resistant S. pneumoniae prevalence (>10%) 1
• Moderate to severe disease 2

High-dose regimens 1:

• Adults: Amoxicillin 2g/clavulanate 125 mg twice daily 1
• Children: Amoxicillin 90 mg/kg/day (maximum 4g daily) with clavulanate 6.4 mg/kg/day divided twice daily 1

Recent research shows conflicting results on high-dose efficacy. One trial found 18% greater improvement at day 3 with immediate-release high-dose formulations 3, but a subsequent trial found no benefit and was stopped for futility 4. Despite this, guidelines continue recommending high-dose therapy for risk factors based on resistance patterns 1, 2.

Penicillin Allergy Alternatives

For patients with penicillin allergy 1, 2:

Second-line options:

• Cefuroxime: 250-500 mg twice daily (adults); 7.5 mg/kg twice daily (children) 1
• Cefpodoxime: 200-400 mg twice daily (adults); 5 mg/kg twice daily (children) 1
• Cefdinir: Available as alternative cephalosporin 1

Important caveat: Recent evidence shows cross-reactivity risk between penicillins and second/third-generation cephalosporins is negligible—no greater than in patients without penicillin allergy 1. Therefore, cephalosporins can be safely used in most penicillin-allergic patients.

For true severe penicillin allergy 1:

• Respiratory fluoroquinolones: Levofloxacin 500-750 mg daily or moxifloxacin 400 mg daily (adults only) 1, 2
• Macrolides: Azithromycin 500 mg day 1, then 250 mg daily for 4 days; or clarithromycin 500 mg twice daily 1

Avoid macrolides when possible due to weak activity against penicillin-resistant S. pneumoniae and increasing resistance 1.

Treatment Duration

Adults: 5-7 days for uncomplicated cases (weak recommendation) 1, 2

Children: 10-14 days (weak recommendation) 1, 2

The shorter adult duration is supported by comparative trials showing equivalent outcomes 1. Some experts suggest treating until symptom-free plus 7 additional days, resulting in minimum 10-day courses 1.

Adjunctive Therapies

Recommended adjuncts 1, 2:

• Intranasal saline irrigation (physiologic or hypertonic): Weak recommendation for adults 1, 2
• Intranasal corticosteroids: Weak recommendation, especially beneficial in patients with allergic rhinitis history 1, 2

NOT recommended (strong recommendation against) 1, 2:

• Oral or topical decongestants 1, 2
• Oral or topical antihistamines 1, 2

Despite theoretical benefits of reducing ostial obstruction, decongestants lack evidence in sinusitis and antihistamines have no demonstrated role in acute bacterial sinusitis 1.

Reassessment and Treatment Failure

Reassess at 48-72 hours if symptoms worsen or at 3-5 days if no improvement 1, 2:

Switch to broader coverage 1:

• High-dose amoxicillin-clavulanate (if not already used) 1
• Respiratory fluoroquinolone (levofloxacin 500-750 mg daily or moxifloxacin 400 mg daily) 1
• Cefuroxime, cefpodoxime, or cefdinir 1

Do NOT routinely cover Staphylococcus aureus or MRSA during initial or second-line therapy (strong recommendation) 1, 2.

Specialist Referral Indications

Refer to otolaryngology, infectious disease, or allergy specialist when 1, 2:

• Seriously ill or toxic-appearing patients 1
• Immunocompromised status 1, 2
• Continued deterioration despite extended antibiotic courses 1, 2
• Recurrent episodes with clearing between bouts 1, 2
• Suspected complications (orbital or intracranial extension) 1

Common Pitfalls

Avoid treating viral rhinosinusitis with antibiotics—symptoms <7 days without severe features or double-sickening pattern are typically viral 1. Inappropriate antibiotic use for viral infections is strongly discouraged 1.

Do not obtain imaging routinely—diagnosis is clinical; CT/MRI reserved for suspected complications or treatment failures 2.

Monitor for severe diarrhea—occurs in 5-15% of patients on amoxicillin-clavulanate, particularly with high-dose formulations 3, 4. Instruct patients to report bloody stools or severe diarrhea immediately due to C. difficile risk 1.