Amoxicillin Dosing for a 2-Year-Old with Acute Otitis Media
Give high-dose amoxicillin at 80-90 mg/kg/day divided into 2 doses daily for 10 days. 1, 2
Dosage Calculation
For a typical 2-year-old (assuming weight of approximately 12-13 kg):
- Calculate 80-90 mg/kg/day × child's weight in kg 1, 2
- Divide the total daily dose into 2 equal doses given 12 hours apart 1, 2
- Example: For a 12 kg child, this equals 960-1080 mg/day total, or approximately 480-540 mg per dose twice daily 2
Rationale for High-Dose Therapy
High-dose amoxicillin is the recommended first-line treatment because it achieves middle ear fluid concentrations that exceed the minimum inhibitory concentration for intermediately resistant Streptococcus pneumoniae for a longer duration. 2
- Approximately 87% of S. pneumoniae isolates are susceptible to high-dose amoxicillin 2
- High-dose therapy eradicates 92% of fully penicillin-resistant S. pneumoniae and 89.7% of H. influenzae (including 85.7% of β-lactamase-positive strains) 3
- Research confirms bacteriologic eradication in 92% of S. pneumoniae cases and 84% of β-lactamase-negative H. influenzae with high-dose amoxicillin 4
Treatment Duration
Treat for 10 days in children under 2 years of age. 2
When to Use Amoxicillin-Clavulanate Instead
Switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin with 6.4 mg/kg/day of clavulanate in 2 divided doses) if: 1, 2
- The child received amoxicillin in the previous 30 days 1, 2
- Concurrent purulent conjunctivitis is present 1, 2
- The child attends daycare (higher risk of β-lactamase-producing organisms) 5
The 14:1 ratio formulation of amoxicillin to clavulanate is preferred as it minimizes gastrointestinal side effects compared to other ratios. 5, 2
Monitoring and Treatment Failure
Clinical improvement should be evident within 48-72 hours. 5, 2
If no improvement occurs within 48-72 hours: 1, 2
- Reassess the diagnosis to confirm acute otitis media
- Switch to high-dose amoxicillin-clavulanate if initially on amoxicillin alone 1, 2
- Consider ceftriaxone (50 mg/kg IM or IV for 3 days) if amoxicillin-clavulanate fails 1
Common Pitfalls to Avoid
The most common cause of treatment failure with high-dose amoxicillin is β-lactamase-producing H. influenzae. 4
- Among bacteriologic failures, 64% are due to β-lactamase-positive H. influenzae 4
- Only 62% of β-lactamase-positive H. influenzae are eradicated with amoxicillin alone, compared to 84% of β-lactamase-negative strains 4
- This is why amoxicillin-clavulanate should be used first-line in children with recent antibiotic exposure or daycare attendance 1, 5
Pain Management
Address pain management regardless of antibiotic choice. 5, 2
Alternative for Vomiting or Oral Intolerance
If the child cannot tolerate oral medication, give a single dose of ceftriaxone 50 mg/kg IM or IV initially. 5