For a 4-year-old child with streptococcal pharyngitis, what is the appropriate amoxicillin dosing, prescription directions (sig), total amount to dispense, and number of refills using a 400 mg/5 mL suspension?

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Last updated: September 21, 2026 • View editorial policy

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Amoxicillin Prescription for 4-Year-Old with Strep Throat

For a 4-year-old child with streptococcal pharyngitis, prescribe amoxicillin 50 mg/kg/day divided into two daily doses for 10 days using the 400 mg/5 mL suspension.

Dosing Calculation

Assuming an average 4-year-old weighs approximately 16-18 kg:

  • Total daily dose: 50 mg/kg/day = 800-900 mg/day
  • Per dose: 400-450 mg twice daily
  • Volume per dose: 5 mL (400 mg) twice daily

If the child weighs more or less, adjust accordingly - the key is 50 mg/kg/day divided into two doses, with each dose not exceeding 500 mg.

Prescription Details

Sig (Directions): Give 5 mL (one teaspoonful) by mouth twice daily for 10 days

Dispense: 100 mL bottle (one bottle is sufficient for the full 10-day course)

  • 5 mL × 2 doses/day × 10 days = 100 mL total

Refills: 0 (zero refills)

Evidence-Based Rationale

The 2012 IDSA guideline for Group A streptococcal pharyngitis specifically recommends amoxicillin 50 mg/kg once daily (max 1000 mg) OR 25 mg/kg (max 500 mg) twice daily for 10 days as first-line therapy 1. The twice-daily dosing at 25 mg/kg per dose (50 mg/kg/day total) is preferred for practical reasons and has strong, high-quality evidence supporting it 1.

Research demonstrates that amoxicillin at 40-50 mg/kg/day achieves superior bacteriologic cure rates (79.3%) compared to standard-dose penicillin V (54.5%, P=0.005) 2. Multiple studies confirm that twice-daily amoxicillin is non-inferior to three-times-daily dosing and provides excellent compliance 3.

Important Clinical Considerations

  • Duration must be 10 days - shorter courses are associated with higher recurrence rates 1
  • Penicillin allergy: If the child has a true penicillin allergy (not just a rash), use cephalexin 20 mg/kg/dose twice daily for 10 days, or clindamycin 7 mg/kg three times daily if there's anaphylactic allergy 1
  • No refills are appropriate - strep pharyngitis is a single acute infection requiring one complete course
  • Compliance is critical - the full 10-day course prevents rheumatic fever, even if symptoms resolve earlier

Common Pitfalls to Avoid

  1. Don't underdose larger children - calculate based on actual weight, not age-based estimates
  2. Don't prescribe azithromycin - it has inferior efficacy (53% vs penicillin) and higher recurrence rates 4
  3. Don't use adult maximum doses prematurely - children can safely receive up to 1000 mg per dose if weight-based dosing indicates it 1
  4. Don't stop at 5-7 days - the 10-day duration is essential for preventing complications 1

The FDA-approved amoxicillin suspension contains 0.15 mEq sodium per 5 mL of the 250 mg formulation, which is negligible for most patients 5. Store reconstituted suspension in the refrigerator and shake well before each use 5.

References

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