Amoxicillin Dosing for 5-Year-Old with Otitis Media (49 lbs)
For this 5-year-old child weighing 49 pounds (22.2 kg) with acute otitis media, prescribe amoxicillin 1000 mg (10 mL of the 400 mg/5 mL suspension) twice daily for 5-7 days, which provides approximately 90 mg/kg/day. 1, 2
Dose Calculation
- Weight conversion: 49 lbs = 22.2 kg
- Recommended dosing: 80-90 mg/kg/day divided into 2 doses 1, 2
- Total daily dose: 1776-1998 mg/day for this child 1, 2
- Practical dosing: 1000 mg (10 mL) twice daily = 2000 mg/day, which equals approximately 90 mg/kg/day 1, 2
Rationale for High-Dose Amoxicillin
High-dose amoxicillin (80-90 mg/kg/day) is the first-line treatment because it provides effective coverage against drug-resistant Streptococcus pneumoniae while maintaining safety, low cost, acceptable taste, and narrow microbiologic spectrum. 1 The American Academy of Pediatrics and American Academy of Family Physicians specifically recommend this higher dosage over standard-dose (40-45 mg/kg/day) due to increasing prevalence of penicillin-resistant S. pneumoniae. 2
Research confirms that standard-dose amoxicillin (40 mg/kg/day) is inadequate to effectively eradicate resistant S. pneumoniae, particularly during viral coinfection, supporting the 75-90 mg/kg/day dosing regimen. 3
Treatment Duration
- For children ≥2 years: 5-7 days is sufficient for uncomplicated acute otitis media 1, 2
- For children <2 years or severe symptoms: Consider 10 days 1
When to Switch Antibiotics
Switch to amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component) if: 1, 2
- The child received amoxicillin in the previous 30 days
- Concurrent purulent conjunctivitis is present
- No improvement at 48-72 hours of treatment
- Coverage for beta-lactamase-producing H. influenzae or M. catarrhalis is needed
The predominant cause of treatment failure with high-dose amoxicillin is beta-lactamase-producing Haemophilus influenzae (62% bacteriologic failure rate), which necessitates switching to a beta-lactamase-stable antibiotic. 4
Reassessment and Pain Management
- Reassess at 48-72 hours if symptoms fail to improve or worsen 1, 2
- Address pain management concurrently during the first 24 hours with appropriate analgesics 1, 2
Common Pitfalls to Avoid
- Underdosing: Using standard-dose (40-45 mg/kg/day) instead of high-dose amoxicillin leads to treatment failures, especially with resistant S. pneumoniae 2, 3
- Incorrect volume calculation: With 400 mg/5 mL suspension, 1000 mg = 10 mL (not 5 mL) 1, 2
- Inadequate follow-up: Failing to reassess at 48-72 hours can miss treatment failures requiring antibiotic change 1, 2