What is the appropriate amoxicillin dosage for a 9-year-old child weighing 36.1 kg with acute otitis media?

Amoxicillin Dosing for a 9-Year-Old with Acute Otitis Media

For this 9-year-old child weighing 36.1 kg with an ear infection, prescribe high-dose amoxicillin 80–90 mg/kg/day divided into two doses for 5–7 days, which translates to 1,450–1,625 mg twice daily (total daily dose 2,900–3,250 mg). 1, 2, 3

Dose Calculation

• Calculate the total daily dose: 36.1 kg × 80 mg/kg = 2,888 mg/day (minimum) or 36.1 kg × 90 mg/kg = 3,249 mg/day (maximum) 1
• Divide into two equal doses given 12 hours apart: approximately 1,450 mg twice daily (using 80 mg/kg/day) or 1,625 mg twice daily (using 90 mg/kg/day) 1, 3
• Maximum single dose is 2,000 mg, so both calculated doses are within safe limits 3

Treatment Duration for This Age Group

• For children ≥6 years with mild-to-moderate acute otitis media, a 5–7 day course is appropriate 2
• If symptoms are severe (moderate-to-severe ear pain, pain lasting ≥48 hours, or fever ≥39°C), extend treatment to a full 10-day course 1, 2

Why High-Dose Amoxicillin?

• High-dose amoxicillin achieves middle ear fluid concentrations that exceed the minimum inhibitory concentration for approximately 87% of Streptococcus pneumoniae isolates, including intermediately resistant strains 1, 3
• It provides adequate coverage against the three principal pathogens: S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis 1, 3
• Twice-daily dosing is as effective as three-times-daily dosing and improves adherence 1, 4

When to Switch to Amoxicillin-Clavulanate Instead

Use amoxicillin-clavulanate (90 mg/kg/day amoxicillin + 6.4 mg/kg/day clavulanate in two divided doses) as first-line therapy if any of the following apply: 1, 2, 3

• The child received amoxicillin within the past 30 days
• Concurrent purulent conjunctivitis is present (suggests H. influenzae)
• The child attends daycare or lives in an area with high prevalence of β-lactamase-producing organisms

Reassessment Protocol

• Reassess at 48–72 hours if symptoms worsen or fail to improve 1, 2
• If amoxicillin fails, switch to amoxicillin-clavulanate (90 mg/kg/day amoxicillin component) 1, 2
• If amoxicillin-clavulanate fails, administer intramuscular ceftriaxone 50 mg/kg once daily for 3 consecutive days 1, 2

Pain Management (Critical First Step)

• Initiate weight-based acetaminophen or ibuprofen immediately for any ear pain, regardless of antibiotic decision 2
• Analgesics provide relief within 24 hours, whereas antibiotics provide no symptomatic benefit in the first 24 hours 2
• Continue pain medication throughout the acute phase 2

Common Pitfalls to Avoid

• Do not use standard-dose amoxicillin (40–45 mg/kg/day) as it provides inadequate coverage for resistant S. pneumoniae 1, 3
• Do not use azithromycin as first-line therapy because pneumococcal macrolide resistance exceeds 40% in the United States, with bacterial failure rates of 20–25% 1
• Do not use trimethoprim-sulfamethoxazole or erythromycin-sulfisoxazole for treatment failures due to substantial resistance 2
• Antibiotics do not prevent complications like acute mastoiditis; 33–81% of mastoiditis patients had received prior antibiotics 2