Amoxicillin Dosing for Strep Throat
For strep throat, use amoxicillin 50 mg/kg once daily (maximum 1000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days in children, and 500 mg twice daily for 10 days in adults. 1
Pediatric Dosing (Children ≥3 months and <40 kg)
The Infectious Diseases Society of America strongly recommends once-daily dosing at 50 mg/kg (maximum 1000 mg) as the preferred regimen, with twice-daily dosing at 25 mg/kg per dose (maximum 500 mg per dose) as an acceptable alternative. 1 Both regimens must be continued for the full 10 days. 1, 2
Why Once-Daily Dosing Works
- Once-daily amoxicillin has proven equivalent efficacy to twice-daily dosing and conventional penicillin given 3-4 times daily, with the major advantage of improved compliance. 3
- Research demonstrates that amoxicillin at 40 mg/kg/day achieves 87.9% clinical cure and 79.3% bacteriologic cure, significantly superior to lower-dose penicillin V (70.9% clinical cure, 54.5% bacteriologic cure). 4
Adult Dosing (≥40 kg)
Adults should receive 500 mg twice daily for 10 days. 1, 2 This is equivalent to the weight-based pediatric dosing when scaled appropriately. 1
Critical Treatment Principles
Complete the full 10-day course regardless of symptom improvement to prevent acute rheumatic fever. 1, 2 This is a "strong, high" recommendation from the Infectious Diseases Society of America. 1
- Patients become non-contagious after 24 hours of appropriate antibiotic therapy, but treatment must continue for the full 10 days to prevent complications. 1
- The FDA label explicitly states: "It is recommended that there be at least 10 days' treatment for any infection caused by Streptococcus pyogenes to prevent the occurrence of acute rheumatic fever." 2
Administration Instructions
Amoxicillin should be taken at the start of a meal to minimize gastrointestinal intolerance. 2
Common Pitfalls to Avoid
- Do NOT use amoxicillin-clavulanate for uncomplicated strep throat. Plain amoxicillin is first-line; amoxicillin-clavulanate is reserved only for recurrent cases or suspected resistance. 1
- Do NOT shorten the course below 10 days, even if symptoms resolve earlier. Shortening the course dramatically increases treatment failure rates and risk of acute rheumatic fever. 1
- Do NOT prescribe doses lower than recommended. The perception that penicillin is declining in effectiveness may be due to inadequate dosing rather than true resistance. 4
Alternative Regimens for Penicillin Allergy
For patients with documented penicillin allergy, alternatives include:
- Cephalexin 20 mg/kg/dose twice daily (maximum 500 mg/dose) for 10 days (for non-immediate allergy only) 1
- Clindamycin 7 mg/kg/dose three times daily (maximum 300 mg/dose) for 10 days 1
- Azithromycin 12 mg/kg once daily (maximum 500 mg) for 5 days 1
- Clarithromycin 7.5 mg/kg/dose twice daily (maximum 250 mg/dose) for 10 days 1