Amoxicillin Dosage for Strep Throat
For strep throat, amoxicillin should be dosed at 50 mg/kg once daily (maximum 1000 mg) or alternatively 25 mg/kg twice daily (maximum 500 mg per dose) for children, and 500 mg twice daily for adolescents and adults, with treatment continued for a full 10 days. 1
Pediatric Dosing
- Children should receive 50 mg/kg once daily (maximum 1000 mg) for 10 days as the preferred regimen. 1, 2
- An alternative dosing schedule is 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days. 1, 2
- Both regimens carry a "Strong, high" recommendation based on quality evidence from the Infectious Diseases Society of America. 1
Adult and Adolescent Dosing
- Adolescents and adults should receive 500 mg twice daily for 10 days. 1, 2
- This dosing provides equivalent efficacy to penicillin V while offering improved convenience. 3
Critical Treatment Principles
- The full 10-day course must be completed even if symptoms resolve earlier, as this is essential to prevent acute rheumatic fever and other suppurative complications. 1, 2, 4
- Patients become non-contagious after 24 hours of antibiotic therapy. 2, 3
- Amoxicillin should be taken at the start of a meal to minimize gastrointestinal intolerance. 4
Evidence Supporting Once-Daily Dosing
The once-daily amoxicillin regimen is supported by robust clinical evidence:
- Once-daily amoxicillin (750-1000 mg based on weight) demonstrates non-inferiority to twice-daily dosing, with bacteriologic failure rates of 20.1% versus 15.5% at early follow-up and superior rates of 2.8% versus 7.1% at later follow-up. 5
- Once-daily amoxicillin shows bacteriologic treatment failure rates of only 5% compared to 11% with penicillin V given three times daily. 6
- Higher-dose amoxicillin (40 mg/kg/day) achieves significantly better clinical cure (87.9% vs 70.9%) and bacteriologic cure (79.3% vs 54.5%) compared to standard-dose penicillin V. 7
Advantages Over Penicillin V
- Amoxicillin has a narrow spectrum of activity with few adverse effects. 2
- Once-daily dosing may improve adherence compared to the 3-4 times daily dosing required for penicillin V. 6, 8
- Meta-analysis confirms that once-daily amoxicillin maintains efficacy, whereas once-daily penicillin shows decreased cure rates (12 percentage points lower). 8
Special Populations
For infants under 3 months (12 weeks):
- Maximum dose is 30 mg/kg/day divided every 12 hours due to incompletely developed renal function. 4
- Treatment duration remains 10 days for streptococcal infections. 4
For patients with severe renal impairment (GFR <30 mL/min):
- Do NOT use the 875 mg dose formulation. 4
- For GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours. 4
- For GFR <10 mL/min: 500 mg or 250 mg every 24 hours. 4
Common Pitfalls to Avoid
- Do not prescribe shortened courses (5-7 days) despite some recent data suggesting potential equivalence, as current guidelines maintain the 10-day standard to prevent rheumatic fever. 1, 9
- Ensure patients understand that symptom resolution does not indicate treatment completion—the full 10-day course prevents serious complications. 1, 2
- Do not confuse amoxicillin dosing with amoxicillin-clavulanate dosing; for uncomplicated strep throat, amoxicillin alone is first-line. 10, 2