Penicillin Dosing for 91-Pound Child with Strep Throat
For a 91-pound (41 kg) child with streptococcal pharyngitis, give 10 mL of penicillin V oral solution (250 mg/5 mL concentration) twice daily for 10 days, which provides approximately 500 mg per dose.
Weight-Based Calculation
- A 91-pound child weighs approximately 41 kg 1
- The recommended dose of penicillin V for streptococcal pharyngitis is 50-75 mg/kg/day divided into 2-4 doses 2, 3
- Using the standard dosing of 250 mg (400,000 units) every 6-8 hours for children, twice-daily dosing is equally effective 4
Specific Milliliter Recommendation
Using the 250 mg/5 mL oral solution concentration:
- Give 10 mL (250 mg) twice daily for 10 days 3
- This provides approximately 12 mg/kg per dose, well within the recommended range 3
The FDA label specifies that for streptococcal infections of the upper respiratory tract, the dose is 125-250 mg (200,000-400,000 units) every 6-8 hours for 10 days 3. For a child of this weight, 250 mg twice daily is appropriate and supported by meta-analysis showing twice-daily penicillin dosing is as efficacious as more frequent dosing 4.
Important Considerations
- Complete the full 10-day course even if symptoms resolve earlier to prevent acute rheumatic fever 1
- Shake the oral solution well before each use and store in refrigerator 3
- The child becomes non-contagious after 24 hours of antibiotic therapy 1
- Twice-daily dosing improves compliance compared to three or four times daily dosing 4
Alternative if Amoxicillin is Preferred
If using amoxicillin instead (which has better compliance and narrow spectrum), give 1000 mg once daily (maximum dose for this weight) or 500 mg twice daily for 10 days 1. This would be 20 mL of 250 mg/5 mL suspension once daily or 10 mL twice daily.
Common Pitfall to Avoid
Do not use once-daily penicillin V dosing - it is associated with a 12 percentage point lower cure rate compared to more frequent dosing 4. Once-daily dosing is only effective with amoxicillin, not penicillin V 5, 4.