What is the first‑line antibiotic choice and dosing for an otherwise healthy child with acute bacterial sinusitis?

First-Line Antibiotic for Pediatric Acute Bacterial Sinusitis

For an otherwise healthy child with acute bacterial sinusitis, amoxicillin at 45 mg/kg/day divided into two doses is the first-line antibiotic choice, with treatment continued for 10-14 days or until symptom-free for 7 days. 1

Standard First-Line Therapy

• Amoxicillin 45 mg/kg/day in 2 divided doses is the preferred initial treatment for children ≥2 years without recent antibiotic exposure, not attending daycare, and with no drug allergies 1, 2
• This regimen provides excellent coverage against Streptococcus pneumoniae (the most common pathogen, accounting for 30-66% of cases), acceptable activity against Haemophilus influenzae (20-30%), and Moraxella catarrhalis (12-28%) 3, 4
• Amoxicillin remains the gold standard due to its proven efficacy, excellent safety profile, acceptable taste for children, low cost, and narrow microbiologic spectrum 2

When to Escalate to High-Dose Therapy

Switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in 2 divided doses) for children with specific risk factors:

• Age <2 years 1, 2
• Daycare attendance 1, 2
• Antibiotic use within the past 4-6 weeks 1, 2
• Geographic areas with high prevalence (>10%) of penicillin-resistant S. pneumoniae 1, 2
• Severe illness at presentation (high fever ≥39°C with purulent discharge for ≥3 consecutive days) 1

The clavulanate component is critical because 10-42% of H. influenzae and nearly 100% of M. catarrhalis produce β-lactamase, rendering them resistant to amoxicillin alone 5, 4

Treatment Duration

• Minimum 10-14 days total or continue for 7 days after the child becomes symptom-free 1, 2
• This individualized approach ensures adequate treatment while avoiding unnecessarily prolonged courses in children who respond quickly 2
• Some experts recommend treating until symptom-free plus an additional 7 days, which typically results in 10-14 days total 5, 6

Critical 72-Hour Reassessment

Reassess every child at 72 hours after starting antibiotics: 1, 2

• If worsening or no improvement: switch immediately to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component) 1, 2
• Treatment failure at this timepoint suggests β-lactamase-producing organisms (H. influenzae or M. catarrhalis) that require clavulanate coverage 2
• Failure to reassess and escalate therapy at 72 hours is a common pitfall that delays effective treatment 1

Alternative for Penicillin Allergy

• Non-severe (non-Type I) allergy: cefdinir, cefuroxime axetil, or cefpodoxime proxetil for 10 days 1, 5, 3
• Severe (Type I/anaphylactic) allergy: levofloxacin or moxifloxacin (though fluoroquinolones are generally avoided in children due to musculoskeletal concerns) 1
• Cross-reactivity between penicillins and second/third-generation cephalosporins is negligible, making cephalosporins safe for most penicillin-allergic children 1

Special Circumstance: Vomiting or Non-Compliance

• Ceftriaxone 50 mg/kg IM or IV as a single dose if the child is vomiting, cannot tolerate oral medications, or is unlikely to take initial doses as prescribed 1, 2
• After clinical improvement with ceftriaxone, switch to oral amoxicillin to complete the 10-14 day course 2

Antibiotics to Avoid

Never use azithromycin or trimethoprim-sulfamethoxazole as first-line therapy: 1, 2

• Resistance rates for S. pneumoniae and H. influenzae to these agents exceed 20-25% 1, 2
• The American Academy of Pediatrics explicitly contraindicates azithromycin for pediatric sinusitis due to these resistance patterns 1

Red Flags Requiring Immediate Escalation

Suspect orbital or intracranial complications if the child develops: 1, 2

• Periorbital swelling, proptosis, or impaired extraocular muscle function 1, 2
• Severe headache, altered mental status, seizures, or focal neurologic findings 2
• These complications require immediate contrast-enhanced CT imaging, IV antibiotics (vancomycin plus ceftriaxone or cefotaxime), and urgent ENT/neurosurgery consultation 1, 2

Common Pitfalls to Avoid

• Do not obtain imaging (CT or MRI) for uncomplicated bacterial sinusitis—imaging does not contribute to diagnosis in straightforward cases and is reserved only for suspected complications 2
• Do not use first-generation cephalosporins (cephalexin)—they provide inadequate coverage against H. influenzae due to β-lactamase production 1
• Do not continue ineffective therapy beyond 72 hours—early reassessment and escalation prevent treatment failure and complications 1, 2