Amoxicillin Dosing for Adult Strep Throat
For adults with streptococcal pharyngitis, prescribe amoxicillin 500 mg orally twice daily for 10 days. 1, 2
Standard Adult Dosing Regimen
The FDA-approved dosing for adults with strep throat is 500 mg every 12 hours OR 250 mg every 8 hours for mild to moderate infections. 2
For more severe infections, the FDA label supports 875 mg every 12 hours or 500 mg every 8 hours. 2
The American Academy of Family Physicians specifically recommends 500 mg twice daily for adolescents and adults with streptococcal pharyngitis. 1
Alternative Once-Daily Dosing
Once-daily amoxicillin at 1000 mg (maximum dose) is an FDA-approved alternative that may improve adherence, recently endorsed by the American Heart Association. 1, 3
Multiple randomized controlled trials demonstrate that once-daily amoxicillin is non-inferior to twice-daily dosing for bacteriologic eradication of Group A Streptococcus. 4, 5
The once-daily regimen showed comparable bacteriologic failure rates (20.1% vs 15.5% at 14-21 days) with no significant difference in adverse events. 5
Critical Treatment Duration
A full 10-day course is absolutely essential to prevent acute rheumatic fever, even if symptoms resolve earlier. 1, 2
The FDA label explicitly states that at least 10 days of treatment is required for any infection caused by Streptococcus pyogenes to prevent acute rheumatic fever. 2
Treatment should continue for a minimum of 48-72 hours beyond symptom resolution or evidence of bacterial eradication. 2
Important Administration Details
Amoxicillin should be taken at the start of a meal to minimize gastrointestinal intolerance. 2
Patients become non-contagious after 24 hours of antibiotic therapy. 1
Renal Dosing Adjustments
Adults with severe renal impairment (GFR <30 mL/min) should NOT receive the 875 mg dose. 2
For GFR 10-30 mL/min: reduce to 500 mg or 250 mg every 12 hours depending on infection severity. 2
For GFR <10 mL/min: reduce to 500 mg or 250 mg every 24 hours. 2
Evidence Quality
The recommended dosing carries a "Strong, high" recommendation based on quality evidence from the American Academy of Family Physicians. 1
Amoxicillin remains first-line due to proven efficacy, narrow spectrum, safety, and low cost. 1
Common Pitfall to Avoid
Do not prescribe shorter courses than 10 days - even a few days' reduction results in appreciable increases in treatment failure rates and rheumatic fever risk. 6
Do not use amoxicillin in patients with immediate/anaphylactic penicillin allergy - these patients require clindamycin or azithromycin instead. 6