Amoxicillin Dosing for 56kg Child with Strep Throat and Otitis Media
For a 56kg child with both streptococcal pharyngitis and acute otitis media, prescribe amoxicillin 400mg/5mL suspension at 1000mg (12.5mL) twice daily for 10 days.
Rationale for This Recommendation
Strep Pharyngitis Dosing
The IDSA guideline 1 recommends amoxicillin 50 mg/kg once daily (maximum 1000 mg) OR 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days as first-line treatment for Group A streptococcal pharyngitis. For this 56kg child:
- Once-daily dosing: 50 mg/kg = 2800 mg, capped at 1000 mg maximum
- Twice-daily dosing: 25 mg/kg = 1400 mg/day total, which equals 700 mg per dose, capped at 500 mg per dose (1000 mg/day total)
Otitis Media Considerations
While the otitis media guideline 2 references amoxicillin dosing at 40-90 mg/kg/day, the standard dose of 40-45 mg/kg/day (2240-2520 mg for 56kg) would far exceed the adult maximum dose. Research shows that primary care physicians appropriately prescribe lower doses in heavier children 3, and that standard-dose amoxicillin is effective for most children at low risk for resistant bacteria 4, 5.
Why Twice-Daily Dosing is Preferred
The twice-daily regimen (1000 mg total daily, given as 500 mg BID) is the most appropriate choice because:
- It provides adequate coverage for both conditions simultaneously
- It stays within FDA-approved maximum adult dosing parameters 6
- Once-daily dosing at 1000 mg may be suboptimal for otitis media, which traditionally requires divided doses
- Twice-daily dosing improves compliance compared to three-times-daily regimens while maintaining efficacy 7
- The 10-day duration is strongly recommended for strep pharyngitis 1 and remains standard for otitis media 2
Practical Prescribing Details
Volume calculation: 500 mg per dose = 6.25 mL of the 400mg/5mL suspension, given twice daily
Total quantity needed: For 10 days (20 doses × 6.25 mL = 125 mL), dispense 150 mL bottle
Key counseling points:
- Shake suspension well before each use
- Use calibrated oral syringe for accurate dosing
- Refrigeration preferred but not required 6
- Complete full 10-day course even if symptoms improve
- Discard unused suspension after 14 days 6
Important Clinical Caveats
Do not exceed adult maximum doses in heavier children. The guideline maximum of 1000 mg/day for strep pharyngitis 1 serves as the ceiling dose regardless of weight-based calculations that might suggest higher amounts.
This recommendation assumes:
- No penicillin allergy
- No recent antibiotic use (which would increase resistance risk)
- No daycare attendance (lower risk for resistant organisms) 5
- Confirmed strep pharyngitis by rapid test or culture 1
If treatment fails at 48-72 hours, consider amoxicillin-clavulanate for broader coverage against beta-lactamase producing organisms, particularly for the otitis media component 2.