Amoxicillin Dosing for Otitis Media in a 5-Year-Old Child
Recommended Dose
For this 5-year-old child weighing 49 pounds (22.3 kg), administer high-dose amoxicillin at 80-90 mg/kg/day divided into 2 doses, which equals approximately 890-1000 mg twice daily (total daily dose 1780-2000 mg). 1
Dosing Calculation
- Weight conversion: 49 pounds = 22.3 kg
- Calculation: 80-90 mg/kg/day × 22.3 kg = 1784-2007 mg/day 1
- Divided dosing: Give approximately 890-1000 mg twice daily (every 12 hours) 1, 2
- Practical formulation: Using amoxicillin suspension 400 mg/5 mL, administer 11-12.5 mL twice daily 1
Rationale for High-Dose Therapy
- High-dose amoxicillin (80-90 mg/kg/day) is the American Academy of Pediatrics' first-line recommendation for acute otitis media in children 1, 2
- This dosing achieves middle ear fluid concentrations that exceed the minimum inhibitory concentration for intermediately resistant Streptococcus pneumoniae for a longer duration of the dosing interval 1, 2
- Approximately 87% of S. pneumoniae isolates are susceptible to high-dose amoxicillin, compared to only 83% for standard-dose therapy 2
- The twice-daily (every 12 hours) regimen is preferred over three-times-daily dosing because it is associated with significantly less diarrhea (14% vs 34%) 1, 3
Treatment Duration and Monitoring
- Duration: Treat for 10 days in children under 6 years of age 2, 3
- Expected response: Clinical improvement should be evident within 48-72 hours 1, 2
- Treatment failure: If no improvement occurs within 48-72 hours, switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day of clavulanate in 2 divided doses) 1, 2
When to Use Amoxicillin-Clavulanate Instead
Do not use plain amoxicillin if any of the following apply:
- Child received amoxicillin in the previous 30 days 4, 1
- Concurrent purulent conjunctivitis is present 4, 1
- Child attends daycare 4
- Moderate to severe illness presentation 4
In these situations, initiate therapy with high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin with 6.4 mg/kg/day of clavulanate, using the 14:1 ratio formulation) 4, 1
Important Clinical Caveats
- Pain management: Address pain regardless of antibiotic choice using appropriate analgesics 4, 2
- Viral coinfection: Amoxicillin middle ear fluid penetration may be reduced in children with concurrent viral infections, though high-dose therapy compensates for this 5
- Beta-lactamase producers: The predominant cause of high-dose amoxicillin failure is beta-lactamase-producing Haemophilus influenzae (62% eradication rate vs 92% for S. pneumoniae), which necessitates switching to amoxicillin-clavulanate 6