Amoxicillin Dosing for Adults with Streptococcal Pharyngitis
For adults with streptococcal pharyngitis, amoxicillin 500 mg twice daily for 10 days is the recommended regimen. 1
Standard Adult Dosing Regimen
Amoxicillin 500 mg orally twice daily (every 12 hours) for 10 days is the established dosing for adolescents and adults with streptococcal pharyngitis. 1
This regimen carries a "Strong, high" recommendation based on quality evidence and represents the preferred first-line treatment for non-allergic patients. 1
The FDA-approved dosing for upper respiratory tract infections in adults ranges from 750 to 1750 mg/day in divided doses every 8 to 12 hours, with the 500 mg twice daily regimen falling within this range. 2
Alternative Once-Daily Dosing Option
Amoxicillin 1000 mg once daily for 10 days is an acceptable alternative regimen that may improve adherence. 3, 1
The American Heart Association has endorsed once-daily amoxicillin dosing for streptococcal pharyngitis, and this regimen has demonstrated equivalent efficacy to twice-daily dosing. 1, 4
Once-daily dosing (750 mg or 1000 mg depending on weight) showed non-inferior bacteriologic failure rates compared to twice-daily dosing in a large controlled trial of 652 patients. 4
Critical Treatment Duration Requirements
A full 10-day course is absolutely essential to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever, even if symptoms resolve earlier. 3, 1
The Centers for Disease Control and Prevention emphasizes that all antibiotics except azithromycin require the complete 10-day course to prevent rheumatic fever. 3
Treatment can be safely postponed up to 9 days after symptom onset and still prevent rheumatic fever, but once started, the full course must be completed. 3
Administration Guidance
Amoxicillin should be taken at the start of a meal to minimize gastrointestinal intolerance. 2
Patients become non-contagious after 24 hours of appropriate antibiotic therapy but must complete the full 10-day course. 3
Advantages of Amoxicillin
Amoxicillin has a narrow spectrum of activity with few adverse effects, making it superior to broader-spectrum alternatives. 1
It remains the first-line option due to proven efficacy, safety, narrow spectrum, and low cost. 1
Once-daily dosing may improve adherence compared to multiple daily doses, with more than 95% of patients complying with 10 days of therapy in clinical trials. 4
Common Pitfalls to Avoid
Never prescribe shorter courses than 10 days (except for azithromycin's 5-day regimen), as this increases treatment failure rates and risk of acute rheumatic fever. 3, 1
Do not use broader-spectrum antibiotics when amoxicillin is appropriate, as this unnecessarily increases cost and promotes antibiotic resistance. 1
Ensure patients understand they must complete the full 10-day course even after symptoms resolve, as premature discontinuation can lead to treatment failure and complications. 3, 1