Amoxicillin Dosing for Streptococcal Pharyngitis
For streptococcal pharyngitis, amoxicillin should be dosed at 50 mg/kg once daily (maximum 1,000 mg) for children or 500 mg twice daily for adolescents and adults, continued for a full 10 days to prevent acute rheumatic fever. 1, 2
Pediatric Dosing
Children should receive 50 mg/kg once daily (maximum 1,000 mg) for 10 days. 1 This once-daily regimen has been endorsed by the American Academy of Family Physicians and demonstrates equivalent efficacy to more frequent dosing while potentially improving adherence 1, 3.
An alternative pediatric dosing is 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1. For severe infections or lower respiratory tract involvement, higher doses of 45 mg/kg/day divided every 12 hours or 40 mg/kg/day divided every 8 hours may be used 2.
Research demonstrates that amoxicillin at 40 mg/kg/day achieves superior bacteriologic cure rates (79.3%) compared to standard-dose penicillin V (54.5%), with significantly better clinical outcomes 4.
Adolescent and Adult Dosing
Adolescents and adults should receive 500 mg twice daily for 10 days. 1 For severe infections, 875 mg every 12 hours or 500 mg every 8 hours is appropriate 2.
The FDA-approved once-daily formulation (Moxatag) at 1,000 mg daily for 10 days is available for patients 12 years and older 5.
Critical Treatment Principles
The full 10-day course must be completed even after symptoms resolve to prevent acute rheumatic fever. 5, 1, 2 This is non-negotiable—treatment started as late as 9 days after symptom onset still effectively prevents rheumatic fever, but the duration cannot be shortened 5.
Patients become non-contagious after 24 hours of antibiotic therapy 5, 1.
Amoxicillin should be taken at the start of a meal to minimize gastrointestinal intolerance 2.
Advantages Over Penicillin V
Amoxicillin offers several practical advantages: once-daily dosing improves adherence 1, 3, the suspension is considerably more palatable than penicillin V (particularly important in young children) 5, and meta-analysis confirms once-daily amoxicillin is not inferior to penicillin V or more frequent amoxicillin dosing 3, 6.
Common Pitfalls to Avoid
Do not use once-daily penicillin V—meta-analysis shows it has 12 percentage points lower cure rates compared to more frequent dosing 6. Once-daily dosing is only validated for amoxicillin, not penicillin V 6.
Do not prescribe 5-day courses as routine therapy. While some retrospective data suggest 5-7 day courses may be effective 7, current guidelines uniformly recommend 10 days, and this shorter duration has not been comprehensively endorsed by major societies 1, 2.
Do not use the 875 mg dose in patients with severe renal impairment (GFR <30 mL/min). 2 These patients require dose reduction to 500 mg or 250 mg every 12-24 hours depending on severity 2.
Penicillin-Allergic Patients
For true penicillin allergy, alternatives include cephalexin 20 mg/kg twice daily (maximum 500 mg per dose) for 10 days, clindamycin 7 mg/kg three times daily (maximum 300 mg per dose) for 10 days, or azithromycin 12 mg/kg once daily (maximum 500 mg) for 5 days 1. However, macrolide resistance varies geographically and is well-documented, making azithromycin less reliable 1.