What is the recommended dosage of amoxicillin (amoxicillin) for strep throat?

Amoxicillin Dosage for Strep Throat

For children, use amoxicillin 50 mg/kg once daily (maximum 1,000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days; for adults, use 875 mg twice daily or 500 mg three times daily for 10 days. 1, 2

Pediatric Dosing

• Weight-based dosing is essential: 50 mg/kg once daily (capped at 1,000 mg) or alternatively 25 mg/kg twice daily (capped at 500 mg per dose) for a full 10-day course 1, 2
• Once-daily dosing significantly improves adherence in children and has comparable efficacy to traditional penicillin V regimens 1
• Amoxicillin is preferred over penicillin V in pediatric patients due to superior palatability and taste acceptance 1
• For infants under 12 weeks (3 months), the maximum dose is 30 mg/kg/day divided every 12 hours due to immature renal function 3

Adult Dosing

• Standard regimen: 875 mg twice daily for 10 days 1
• Alternative regimen: 500 mg three times daily for 10 days 1, 3
• Once-daily option: 1,000 mg once daily for 10 days may be used to enhance adherence 1

Critical Duration Requirement

• Complete the full 10-day course regardless of symptom improvement to prevent acute rheumatic fever, a potentially devastating complication of inadequately treated Group A Streptococcus pharyngitis 1, 2, 3
• The Infectious Diseases Society of America gives this recommendation a "strong, high" evidence rating 2
• Patients become non-contagious after 24 hours of antibiotic therapy, but this does NOT justify early discontinuation 2
• Treatment should continue for a minimum of 48-72 hours beyond symptom resolution, but the 10-day minimum must be met for streptococcal infections 3

Evidence Supporting Dosing Recommendations

The higher-dose amoxicillin regimen (40-50 mg/kg/day) demonstrates superior bacteriologic eradication compared to standard-dose penicillin V, with one study showing 79.3% vs 54.5% negative throat cultures (P = 0.005) and significantly lower carrier rates 4. Once-daily amoxicillin dosing has been validated through meta-analysis as non-inferior to multiple-daily-dose regimens of amoxicillin or penicillin V 5.

Penicillin Allergy Alternatives

If documented penicillin allergy exists, consider these alternatives 2:

• Cephalexin: 20 mg/kg/dose twice daily (maximum 500 mg/dose) for 10 days
• Clindamycin: 7 mg/kg/dose three times daily (maximum 300 mg/dose) for 10 days
• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days (note: geographic macrolide resistance varies)
• Clarithromycin: 7.5 mg/kg/dose twice daily (maximum 250 mg/dose) for 10 days

Important Clinical Pitfalls

• Do not use amoxicillin-clavulanate for uncomplicated strep throat—plain amoxicillin is first-line; the combination is reserved only for recurrent cases or suspected resistance 2
• Avoid shortened antibiotic courses: While some research suggests 5-7 day courses may be adequate 6, current guidelines strongly recommend 10 days based on decades of evidence preventing rheumatic fever 1, 2
• Do not routinely perform post-treatment throat cultures unless special circumstances exist (e.g., history of rheumatic fever, outbreak situations) 1
• Patients with severe renal impairment (GFR <30 mL/min) should NOT receive the 875 mg dose and require dose adjustment 3

Administration Considerations

• Administer at the start of meals to minimize gastrointestinal intolerance 3
• Oral suspension can be mixed with formula, milk, fruit juice, water, or cold drinks for children, but must be consumed immediately after mixing 3
• Reconstituted suspension remains stable for 14 days; refrigeration is preferable but not required 3