Amoxicillin Dosing for 11-Year-Old Male with Strep Throat
For an 11-year-old male with streptococcal pharyngitis, give amoxicillin 50 mg/kg once daily (maximum 1000 mg) for 10 days, which translates to approximately 20 mL once daily if using standard 250 mg/5 mL suspension, assuming an average weight of 35-40 kg for this age. 1
Specific Dosing Calculation
Weight-based dosing:
- 50 mg/kg once daily (maximum 1000 mg) for 10 days 1
- Alternative: 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1
Converting to mL (using standard 250 mg/5 mL suspension):
- For a 35 kg child: 50 mg/kg = 1750 mg ÷ 250 mg per 5 mL = 35 mL once daily (but capped at maximum 1000 mg = 20 mL once daily)
- For a 40 kg child: 50 mg/kg = 2000 mg, but maximum is 1000 mg = 20 mL once daily
- Most 11-year-olds will receive 20 mL once daily (1000 mg maximum dose) 1
If using twice-daily dosing:
- 25 mg/kg twice daily = approximately 10 mL twice daily for most 11-year-olds (500 mg per dose maximum) 1
Why This Regimen
Once-daily dosing is equally effective to multiple daily doses:
- Large randomized controlled trials demonstrate once-daily amoxicillin is non-inferior to twice-daily dosing, with bacteriologic failure rates of 20.1% vs 15.5% at 14-21 days and 2.8% vs 7.1% at 28-35 days 2
- Once-daily dosing improves compliance with >95% adherence rates 2
- Real-time PCR studies confirm once-daily dosing achieves equivalent bacterial eradication as multiple daily doses 3
Amoxicillin is first-line therapy:
- The Infectious Diseases Society of America and American Academy of Pediatrics recommend amoxicillin or penicillin as first-line treatment due to proven efficacy, narrow spectrum, safety, and low cost 1
- No documented penicillin resistance in Group A Streptococcus has ever been reported 1
- Amoxicillin is often preferred over penicillin V in children due to better palatability of the suspension 4
Critical Treatment Duration
The full 10-day course is mandatory:
- A complete 10-day course achieves maximal pharyngeal eradication of Group A Streptococcus and prevents acute rheumatic fever 1, 5
- Shortening the course even by a few days dramatically increases treatment failure rates and rheumatic fever risk 1, 5
- This applies regardless of symptom improvement, which typically occurs within 3-4 days 6
Common Pitfalls to Avoid
Do not stop early despite clinical improvement:
- Symptoms resolve quickly, but bacterial eradication requires the full 10 days 1
- The primary goal is preventing acute rheumatic fever, not just symptom relief 5
Do not use broad-spectrum alternatives unnecessarily:
- Broad-spectrum cephalosporins (cefdinir, cefixime) are more expensive and increase selection pressure for resistant bacteria 1, 5
- Reserve alternatives only for true penicillin allergy 1
Ensure accurate weight-based dosing:
- Underdosing increases treatment failure risk 1
- The 1000 mg maximum daily dose applies to children weighing ≥20 kg 1
Adjunctive Symptomatic Management
For fever and pain:
- Acetaminophen or NSAIDs (ibuprofen) for moderate to severe symptoms 1
- Never use aspirin in children due to Reye's syndrome risk 1, 5
- Medicated throat lozenges every 2 hours are effective 7
Corticosteroids are not recommended: