Amoxicillin Prescription for 4-Year-Old with Strep Pharyngitis (19 kg)
Prescribe amoxicillin 50 mg/kg once daily (950 mg/day, rounded to 1000 mg once daily) for 10 days, dispense 100 mL of 250 mg/5 mL suspension, with zero refills.
Dosing Rationale
For Group A streptococcal pharyngitis in children, the IDSA guidelines provide strong, high-quality evidence supporting 50 mg/kg once daily (maximum 1000 mg) as the preferred dosing regimen 1, 2. An alternative is 25 mg/kg twice daily (maximum 500 mg per dose), also with strong, high-quality evidence 2.
For this 19 kg child:
- 50 mg/kg/day = 950 mg/day (round to 1000 mg once daily, which is the maximum)
- Alternative: 25 mg/kg twice daily = 475 mg/day (round to 500 mg divided as 250 mg twice daily)
The once-daily regimen is preferred because it improves compliance while maintaining equivalent efficacy to multiple daily dosing 3, 4. Research demonstrates that once-daily amoxicillin achieves comparable bacterial eradication rates and clinical cure rates to twice or three-times daily dosing 3.
Sig (Directions)
"Give 20 mL (1000 mg) by mouth once daily for 10 days"
- Administer at the start of a meal to minimize gastrointestinal intolerance 5
- Shake suspension well before each use 5
- Complete the full 10-day course even if symptoms improve earlier
Dispense Amount
Dispense: 100 mL bottle of amoxicillin 250 mg/5 mL oral suspension
Calculation:
- 20 mL/day × 10 days = 200 mL total needed
- One 100 mL bottle will not suffice; dispense TWO 100 mL bottles or ONE 150 mL bottle if available
Corrected: Dispense 150 mL bottle (or two 100 mL bottles) of 250 mg/5 mL suspension
Refills
Zero refills
Group A streptococcal pharyngitis requires exactly 10 days of treatment to prevent acute rheumatic fever 2, 5. No refills should be provided as this is a single-course treatment.
Critical Treatment Points
Duration is Non-Negotiable
At least 10 days of treatment is mandatory for any Group A streptococcal infection to prevent acute rheumatic fever 2, 5. This is supported by strong, high-quality evidence from IDSA guidelines.
FDA-Approved Dosing Alignment
The FDA label confirms that for ear/nose/throat infections (which includes pharyngitis) in children weighing less than 40 kg, the recommended dose for mild/moderate infections is 25 mg/kg/day divided every 12 hours or 20 mg/kg/day divided every 8 hours 5. However, IDSA guidelines specifically for strep pharyngitis recommend the higher 50 mg/kg once daily regimen 2, which takes precedence as disease-specific guidance.
Common Pitfalls to Avoid
Underdosing larger children: Research shows that as children's weight increases, they often receive progressively lower mg/kg doses, potentially leading to treatment failure 6. This 19 kg child should receive the full 50 mg/kg/day.
Premature discontinuation: Emphasize to caregivers that the full 10-day course must be completed even when symptoms resolve (typically within 48-72 hours) 5.
Confusion with high-dose amoxicillin: The 80-90 mg/kg/day "high-dose" regimen is for pneumococcal infections (pneumonia, otitis media) 7, 8, not for strep pharyngitis. For strep throat, 50 mg/kg/day is appropriate and guideline-recommended 2.
Storage Instructions
After reconstitution, the suspension remains stable for 14 days. Refrigeration is preferable but not required 5. Any unused portion after 14 days must be discarded.
Expected Clinical Response
Patients should show clinical improvement within 48-72 hours 5. If fever persists beyond 3 days or symptoms worsen, re-evaluation is necessary to assess for complications (peritonsillar abscess, cervical lymphadenitis) or alternative diagnoses.