Amoxicillin Dosing for Strep Throat
For children with strep throat, give amoxicillin 50 mg/kg once daily (maximum 1000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for a full 10 days; for adults, give 500 mg twice daily or 875 mg twice daily for 10 days. 1, 2
Pediatric Dosing
- The preferred regimen is 50 mg/kg once daily (maximum 1000 mg) for 10 days, which improves adherence while maintaining comparable efficacy to traditional penicillin V 1, 2
- An alternative is 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1, 2
- Once-daily dosing is non-inferior to twice-daily dosing and significantly improves compliance, with >95% of patients completing the full 10-day course 3
- Amoxicillin is often preferred over penicillin V in children due to better taste acceptance 1
Adult Dosing
- Standard dose is 500 mg twice daily for 10 days 2
- Alternative regimen is 875 mg twice daily for 10 days 1
- A once-daily option of 1000 mg for 10 days is also acceptable 1
Critical Treatment Duration
- Complete the full 10-day course regardless of symptom improvement to ensure complete eradication of Group A Streptococcus and prevent acute rheumatic fever 1, 2
- Patients become non-contagious after 24 hours of appropriate antibiotic therapy, but treatment must continue for the full 10 days to prevent complications 2
- Shortening the course by even a few days results in appreciable increases in treatment failure rates 4
Evidence Supporting Higher Amoxicillin Doses
- Amoxicillin at 40 mg/kg/day (equivalent to the recommended 50 mg/kg once daily or 25 mg/kg twice daily) was significantly more effective than lower-dose penicillin V for both clinical cure (87.9% vs 70.9%, P=0.025) and bacteriologic cure (79.3% vs 54.5%, P=0.005) 5
- The carrier rate was also significantly lower with amoxicillin (10.3% vs 23.6%) 5
- The current perception that penicillin is declining in effectiveness may be due to inadequate dosing 5
Common Pitfalls to Avoid
- Do not prescribe shorter courses than 10 days - inadequate duration increases risk of treatment failure, rheumatic fever, and post-streptococcal glomerulonephritis 1, 2
- Do not use amoxicillin-clavulanate for uncomplicated strep throat - plain amoxicillin is first-line; amoxicillin-clavulanate is reserved for recurrent cases or suspected resistance 2
- Do not routinely perform post-treatment throat cultures in asymptomatic patients who have completed therapy unless there are special circumstances such as history of rheumatic fever 1, 4
Alternative Regimens for Penicillin Allergy
- For non-immediate penicillin allergy: First-generation cephalosporins (cephalexin 20 mg/kg twice daily, maximum 500 mg/dose, for 10 days) are preferred 2, 4
- For immediate/anaphylactic penicillin allergy: Clindamycin 7 mg/kg three times daily (maximum 300 mg/dose) for 10 days is preferred, with ~1% resistance rate in the US 2, 4
- Azithromycin 12 mg/kg once daily (maximum 500 mg) for 5 days is acceptable but has 5-8% macrolide resistance in the US 2, 4
- Clarithromycin 7.5 mg/kg twice daily (maximum 250 mg/dose) for 10 days is also an option 2