What is the appropriate amoxicillin dosing regimen for an otherwise healthy 19‑month‑old child with acute otitis media?

Amoxicillin Dosing for Acute Otitis Media in a 19-Month-Old

Prescribe high-dose amoxicillin at 80–90 mg/kg/day divided into two doses (given every 12 hours) for a 10-day course. 1, 2

Calculating the Exact Dose

• Multiply the child's weight in kilograms by 80–90 mg to get the total daily dose, then divide by 2 to determine each individual dose. 2
• For example, if the child weighs 11 kg: 11 kg × 80 mg/kg = 880 mg/day total, giving 440 mg twice daily; or 11 kg × 90 mg/kg = 990 mg/day total, giving 495 mg twice daily. 2
• Administer the two doses approximately 12 hours apart. 1, 2

Rationale for High-Dose Therapy

• 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), compared with only 83% coverage using standard 40–45 mg/kg/day dosing. 2, 3
• This regimen provides adequate coverage against the three principal bacterial pathogens causing acute otitis media: S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 2
• Amoxicillin remains first-line therapy because it is safe, inexpensive, has acceptable taste, and maintains a narrow microbiologic spectrum. 1

When to Use Amoxicillin-Clavulanate Instead

Switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate in a 14:1 ratio, divided twice daily) if any of the following apply: 1, 2

• The child received amoxicillin within the previous 30 days 1, 2
• Concurrent purulent conjunctivitis is present 1, 2
• The child attends daycare (higher risk of β-lactamase-producing organisms) 3

The 14:1 formulation causes significantly less diarrhea than older 7:1 preparations while maintaining efficacy against β-lactamase-producing H. influenzae and M. catarrhalis. 2, 3

Treatment Duration and Monitoring

• Treat for 10 days in children younger than 2 years of age. 2, 3
• Reassess the child at 48–72 hours if symptoms do not improve or worsen. 1, 3
• Address pain management during the first 24 hours regardless of antibiotic choice, using acetaminophen or ibuprofen. 1, 3

Management of Treatment Failure

If no clinical improvement occurs within 48–72 hours on amoxicillin alone: 1, 3

1. First, confirm the diagnosis of acute otitis media by re-examining the tympanic membrane for bulging, limited mobility, air-fluid level, or otorrhea. 1
2. If the diagnosis is confirmed and the initial regimen was amoxicillin alone, switch to high-dose amoxicillin-clavulanate (90 mg/kg/day amoxicillin + 6.4 mg/kg/day clavulanate, 14:1 ratio, twice daily). 1, 3
3. If failure persists after amoxicillin-clavulanate, administer intramuscular ceftriaxone 50 mg/kg/day for 3 days. 1, 3

Common Pitfalls to Avoid

• Do not use standard-dose amoxicillin (40–45 mg/kg/day) as first-line therapy, as it provides inadequate coverage against resistant S. pneumoniae. 1, 2
• Avoid trimethoprim-sulfamethoxazole or erythromycin-sulfisoxazole for treatment failures, as pneumococcal resistance to these agents is high. 3
• Do not prescribe antibiotics for isolated tympanic membrane redness with normal landmarks or for otitis media with effusion (persistent middle ear fluid without acute symptoms). 3
• Twice-daily dosing improves adherence compared to three-times-daily regimens and has equivalent efficacy. 4