Amoxicillin Dosing for 75-Pound Pediatric Patient with Otitis Media
For a 75-pound (34 kg) child with otitis media, prescribe high-dose amoxicillin at 80-90 mg/kg/day divided into 2 doses, which equals 2720-3060 mg/day (1360-1530 mg twice daily), but this should be capped at the maximum safe daily dose of 4000 mg/day (2000 mg twice daily). 1
Weight Conversion and Dose Calculation
- 75 pounds = 34 kg 1
- High-dose amoxicillin for otitis media: 80-90 mg/kg/day divided into 2 doses 2, 1
- Calculated dose: 34 kg × 80-90 mg/kg = 2720-3060 mg/day 1
- Practical dosing: 1360-1530 mg twice daily (every 12 hours) 1
- This dose is well below the 4000 mg/day maximum, so the full weight-based dose can be safely administered 1
Rationale for High-Dose Therapy
- High-dose amoxicillin (80-90 mg/kg/day) is specifically recommended by the American Academy of Pediatrics (AAP) for otitis media to achieve adequate middle ear fluid concentrations against drug-resistant Streptococcus pneumoniae 2, 1
- Approximately 87% of S. pneumoniae isolates are susceptible to high-dose amoxicillin versus only 83% for standard-dose therapy 1
- Middle ear fluid concentrations peak at approximately 3 hours after dosing, with mean concentrations of 9.5 mcg/mL at the 75-90 mg/kg/day dosing range 3
Tablet Formulation Considerations
- Using 500 mg tablets: The child would need approximately 3 tablets twice daily (1500 mg per dose) to achieve the target dose 1
- This is practical and achievable with standard 500 mg tablets 1
- Treatment duration: 5-10 days depending on severity and clinical response 1
Risk Factors That Support High-Dose Therapy
High-dose amoxicillin is particularly indicated if this child has: 2
- Age younger than 2 years
- Attendance at child care
- Receipt of antimicrobial treatment within the previous 30 days
- Moderate to severe illness presentation
Alternative if Treatment Fails
- If no improvement within 48-72 hours, switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day clavulanate, divided into 2 doses) 2, 1
- For this 34 kg child: 3060 mg amoxicillin + 218 mg clavulanate daily 2
- If persistent failure after amoxicillin-clavulanate, consider intramuscular ceftriaxone 50 mg/kg/day for 3-5 days 1
Common Pitfalls to Avoid
- Do not use standard-dose amoxicillin (40-45 mg/kg/day) for otitis media in the current era of antibiotic resistance 2, 4
- The standard dose of 40 mg/kg/day is inadequate to effectively eradicate resistant S. pneumoniae, particularly during viral coinfection 3
- Do not exceed 4000 mg/day total dose even if weight-based calculations suggest higher amounts 1
- Ensure pain management is addressed regardless of antibiotic choice 1
Evidence Quality Note
The recommendation for high-dose amoxicillin comes from high-quality AAP/AAFP guidelines 2, 1 and is supported by pharmacokinetic studies demonstrating adequate middle ear fluid penetration at these doses 3. Research shows that high-dose amoxicillin achieves bacteriologic eradication in 92% of S. pneumoniae cases and 84% of beta-lactamase-negative H. influenzae cases 5.