Amoxicillin Dosing for Strep Throat
For adults with strep throat, amoxicillin 500 mg twice daily for 10 days is the recommended dose; for children, 50 mg/kg once daily (maximum 1000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days is recommended. 1, 2
Adult Dosing
- Amoxicillin 500 mg orally twice daily for 10 days is the standard regimen for adults with streptococcal pharyngitis 1, 2
- Alternative adult dosing includes 250 mg three times daily for 10 days, though twice-daily dosing improves compliance 1
- The full 10-day course is essential to prevent acute rheumatic fever, even if symptoms resolve within 3-4 days 1, 3
Pediatric Dosing
- 50 mg/kg once daily (maximum 1000 mg) for 10 days is the preferred pediatric regimen with strong, high-quality evidence 1, 2
- Alternative pediatric dosing: 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1, 2
- Once-daily dosing significantly improves adherence compared to multiple daily doses 2, 4
- For infants under 3 months, the maximum dose is 30 mg/kg/day divided every 12 hours due to immature renal function 3
Why Amoxicillin Over Penicillin V
Amoxicillin is often preferred over penicillin V for several practical reasons:
- Better palatability of the suspension formulation for young children 1
- Equivalent efficacy to penicillin V with comparable bacteriologic eradication rates 1, 4
- Once-daily dosing option improves compliance without sacrificing efficacy 2, 4, 5
- Narrow spectrum of activity with few adverse effects 2
Critical Treatment Requirements
- Complete the full 10-day course regardless of symptom resolution to achieve maximal pharyngeal eradication and prevent acute rheumatic fever 1, 2, 3
- Patients become non-contagious after 24 hours of antibiotic therapy and can return to school/work if afebrile and improved 6, 7
- Take amoxicillin at the start of a meal to minimize gastrointestinal intolerance 3
Evidence Supporting Once-Daily Dosing
Recent high-quality evidence demonstrates that once-daily amoxicillin is as effective as multiple-daily dosing:
- Real-time PCR studies show no difference in bacterial eradication between once-daily, twice-daily, or three-times-daily regimens 5
- Clinical trials demonstrate 83-91% bacteriologic eradication rates with once-daily dosing, comparable to traditional regimens 4, 5
- A single dose of amoxicillin (50 mg/kg) results in non-detection of GAS in 91% of children by the next morning 7
Common Pitfalls to Avoid
- Do not shorten the course below 10 days even if symptoms resolve—this dramatically increases treatment failure rates and rheumatic fever risk 1, 2
- Do not use once-daily dosing below the recommended 50 mg/kg—lower doses (such as 1000 mg once daily in adults without weight-based calculation) have shown inferior eradication rates 8
- Do not prescribe amoxicillin for penicillin-allergic patients with immediate/anaphylactic reactions—cross-reactivity risk is up to 10% with all beta-lactams 1, 9
Alternative Regimens for Penicillin Allergy
For patients with non-immediate penicillin allergy (delayed rash, non-anaphylactic):
- Cephalexin 500 mg twice daily for 10 days (adults) or 20 mg/kg twice daily for 10 days (children) 1, 9
For patients with immediate/anaphylactic penicillin allergy: