What is the recommended dose of antibiotics for bacterial pharyngitis?

Antibiotic Dosing for Bacterial Pharyngitis

For adults with streptococcal pharyngitis, penicillin V 500 mg twice daily or 250 mg four times daily for 10 days is the first-line treatment, while children should receive amoxicillin 50 mg/kg once daily (maximum 1,000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days. 1, 2

First-Line Treatment by Age Group

Adults

• Penicillin V: 500 mg twice daily OR 250 mg four times daily for 10 days 1
• Amoxicillin (alternative): 500 mg twice daily for 10 days 1
• Both regimens have proven efficacy, safety, narrow spectrum, and low cost 1

Children and Adolescents

• Amoxicillin: 50 mg/kg once daily (maximum 1,000 mg) OR 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 2
• Once-daily dosing may improve adherence while maintaining equivalent efficacy 2, 3
• The American Heart Association has endorsed once-daily amoxicillin dosing 2

Critical Treatment Duration Requirement

All antibiotics except azithromycin require a full 10-day course to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever. 4, 1, 2

• Shortening the course by even a few days results in appreciable increases in treatment failure rates 4
• Symptoms typically resolve within 3-4 days, but full course completion is essential for preventing complications 4
• Patients become non-contagious after 24 hours of antibiotic therapy 1

Penicillin-Allergic Patients

Non-Immediate/Non-Anaphylactic Allergy

First-generation cephalosporins are preferred first-line alternatives 4, 1

Adults:

• Cephalexin: 500 mg twice daily for 10 days 1
• Cefadroxil: 1 g once daily for 10 days 1

Children:

• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days 4
• Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days 4

Immediate/Anaphylactic Penicillin Allergy

Avoid all beta-lactams including cephalosporins due to up to 10% cross-reactivity risk 4

Adults:

• Clindamycin: 300 mg three times daily for 10 days 1
• Azithromycin: 500 mg on day 1, then 250 mg daily for days 2-5 1
• Clarithromycin: 250 mg twice daily for 10 days 1

Children:

• Clindamycin: 7 mg/kg per dose three times daily (maximum 300 mg/dose) for 10 days 4
• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 4, 5
• Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg/dose) for 10 days 4

Important Considerations for Macrolides

• Azithromycin is the only antibiotic requiring only 5 days of treatment due to its prolonged tissue half-life 4, 1
• Macrolide resistance among Group A Streptococcus ranges from 5-8% in the United States, though this varies geographically 4, 1
• Clindamycin resistance is approximately 1% in the United States 4
• Be aware of local resistance patterns when prescribing macrolides 4

Parenteral Option for Non-Compliant Patients

For patients unlikely to complete a full 10-day oral course, intramuscular benzathine penicillin G 1.2 million units as a single dose is preferred 1

Common Pitfalls to Avoid

• Do NOT prescribe shorter courses than recommended (except azithromycin's 5-day regimen) - this leads to treatment failure and complications 4
• Do NOT assume all penicillin-allergic patients cannot receive cephalosporins - only those with immediate/anaphylactic reactions should avoid them 4
• Do NOT use cephalosporins in patients with immediate hypersensitivity due to 10% cross-reactivity risk 4
• Do NOT use trimethoprim-sulfamethoxazole for strep throat due to high resistance rates (50%) 4
• Do NOT routinely perform follow-up throat cultures for asymptomatic patients who have completed therapy 4, 1

Adjunctive Therapy

• Acetaminophen or NSAIDs (such as ibuprofen) for moderate to severe symptoms or high fever 4
• Avoid aspirin in children due to Reye syndrome risk 4
• Corticosteroids are NOT recommended as adjunctive therapy 4