Amoxicillin Dosing for Tonsillitis (Group A Streptococcal Pharyngitis)
For adults and adolescents, prescribe amoxicillin 500 mg twice daily for 10 days; for children, prescribe 50 mg/kg once daily (maximum 1000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days. 1
Recommended Dosing Regimens
Pediatric Dosing
- 50 mg/kg once daily (maximum 1000 mg) for 10 days 1
- Alternative: 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1
- Both regimens have strong, high-quality evidence supporting their efficacy 1
Adult Dosing
- 250 mg four times daily OR 500 mg twice daily for 10 days 1
- The twice-daily regimen significantly improves compliance while maintaining equivalent efficacy 1, 2
Why These Doses Are Recommended
The full 10-day course is essential to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever 1, 3. Amoxicillin is recommended as first-line therapy because it is generally effective against susceptible and intermediate-resistant pneumococci, safe, inexpensive, has acceptable taste, and has a narrow microbiologic spectrum 1.
Meta-analysis confirms that twice-daily dosing of amoxicillin maintains equivalent cure rates to more frequent dosing schedules, unlike penicillin V where once-daily dosing shows decreased efficacy 2.
Critical Treatment Duration
- Never shorten the 10-day course, even if symptoms resolve earlier (typically within 3-4 days) 3
- Shortening the course by even a few days results in appreciable increases in treatment failure rates and risk of acute rheumatic fever 3
- The primary goal is not just symptomatic improvement but prevention of acute rheumatic fever, which requires adequate bacterial eradication 3
When NOT to Use Standard Amoxicillin
Switch to high-dose amoxicillin-clavulanate (90 mg/kg/day of amoxicillin with 6.4 mg/kg/day of clavulanate in 2 divided doses) if the patient: 1
- Has taken amoxicillin in the previous 30 days
- Has concurrent purulent conjunctivitis (otitis-conjunctivitis syndrome)
- Requires coverage for beta-lactamase producing organisms
Common Pitfalls to Avoid
- Do not prescribe once-daily amoxicillin dosing in adults—unlike twice-daily regimens, once-daily dosing has not been adequately validated for streptococcal pharyngitis 2
- Do not use amoxicillin for penicillin-allergic patients with immediate/anaphylactic reactions (hives, angioedema, bronchospasm within 1 hour), as cross-reactivity risk is significant 3
- Do not stop treatment early based on clinical improvement—bacterial eradication requires the full course 3
Alternative Antibiotics (If Amoxicillin Cannot Be Used)
For non-immediate penicillin allergy: First-generation cephalosporins (cephalexin 500 mg twice daily for 10 days in adults; 20 mg/kg/dose twice daily in children) 1, 3
For immediate/anaphylactic penicillin allergy: 1, 3
- Clindamycin 300 mg three times daily for 10 days (adults) or 7 mg/kg/dose three times daily (children, maximum 300 mg/dose)
- Azithromycin 500 mg once daily for 5 days (adults) or 12 mg/kg once daily (children, maximum 500 mg)—note 5-8% macrolide resistance in the US