Amoxicillin Dosing for Strep Throat
For strep throat, use amoxicillin 50 mg/kg once daily (maximum 1000 mg) or alternatively 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days. 1
Dosing by Age Group
Children and Adolescents
- Preferred regimen: 50 mg/kg once daily (maximum 1000 mg) for 10 days 1
- Alternative regimen: 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1
- Both regimens carry a "strong, high" recommendation from the Infectious Diseases Society of America 1
Adults
- Standard dose: 500 mg twice daily for 10 days 1
- This is equivalent to the weight-based pediatric dosing when scaled appropriately 1
Critical Treatment Principles
Duration is Non-Negotiable
- Complete the full 10-day course regardless of symptom improvement to prevent acute rheumatic fever 1, 2
- This duration applies to all streptococcal pharyngitis cases, even when patients feel better after 2-3 days 1, 2
When Patients Become Non-Contagious
- Patients are no longer contagious after 24 hours of appropriate antibiotic therapy 3
- However, treatment must continue for the full 10 days to prevent complications 1, 2
Evidence Supporting Higher Doses
Research demonstrates that higher amoxicillin doses (40 mg/kg/day) achieve superior clinical and bacteriologic cure rates compared to standard penicillin V dosing 4. In a randomized study of 113 children, amoxicillin 40 mg/kg/day achieved 87.9% clinical cure versus 70.9% with penicillin (p=0.025), and 79.3% bacteriologic cure versus 54.5% with penicillin (p=0.005) 4. The carrier rate was also significantly lower with amoxicillin (10.3% vs 23.6%) 4.
Common Pitfalls to Avoid
Do NOT Use Amoxicillin-Clavulanate for Uncomplicated Strep
- Plain amoxicillin is first-line for uncomplicated streptococcal pharyngitis 1, 3
- Amoxicillin-clavulanate is reserved for recurrent cases or suspected resistance 3
- The clavulanate component adds no benefit against Group A Streptococcus and increases side effects 3
Dosing Errors to Avoid
- Do NOT substitute two 250 mg tablets for one 500 mg tablet when using combination products, as this doubles the clavulanate dose unnecessarily 5
- Ensure adequate dosing: the perception that penicillins are "losing effectiveness" may actually reflect inadequate dosing rather than true resistance 4
Alternative Regimens for Penicillin Allergy
If the patient has a documented penicillin allergy:
- Cephalexin: 20 mg/kg/dose twice daily (maximum 500 mg/dose) for 10 days 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, though resistance is documented 1
- Clarithromycin: 7.5 mg/kg/dose twice daily (maximum 250 mg/dose) for 10 days 1
Note that macrolide resistance varies geographically and temporally, making them less reliable alternatives 1. Ten-day macrolide courses are more effective than 5-day courses for bacterial eradication (91% vs 82%, p=0.012) 6.