What is the recommended antibiotic regimen for treating strep throat?

Treatment of Strep Throat

For patients without penicillin allergy, use penicillin V (250 mg four times daily or 500 mg twice daily) or amoxicillin (50 mg/kg once daily, maximum 1000 mg) for 10 days as first-line treatment. 1

First-Line Treatment Algorithm

For non-allergic patients:

• Penicillin V remains the drug of choice due to proven efficacy, narrow spectrum, safety, and low cost, with no documented resistance anywhere in the world 2, 1
• Dosing options: 250 mg four times daily OR 500 mg twice daily for 10 days 1
• Amoxicillin is equally effective and often preferred at 50 mg/kg once daily (maximum 1000 mg) for 10 days due to better palatability and once-daily dosing 1, 3
• For adolescents/adults: amoxicillin 500 mg twice daily for 10 days 3

Intramuscular benzathine penicillin G (600,000 units if <27 kg; 1,200,000 units if ≥27 kg) as a single dose ensures compliance and is preferred when adherence to oral therapy is uncertain 1

Treatment for Penicillin-Allergic Patients

Critical first step: Determine the type of penicillin allergy 2

Non-Immediate (Non-Anaphylactic) Penicillin Allergy:

• First-generation cephalosporins are the preferred alternatives with strong, high-quality evidence 2, 1
• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg per dose) for 10 days 2, 1
• Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days 2
• Cross-reactivity risk is only 0.1% in patients with non-severe, delayed penicillin reactions 2

Immediate/Anaphylactic Penicillin Allergy:

• Avoid ALL beta-lactam antibiotics (including cephalosporins) due to up to 10% cross-reactivity risk 2, 1
• Clindamycin is the preferred choice: 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days 2, 1
• Clindamycin has strong, moderate-quality evidence with approximately 1% resistance rate in the United States 2
• Particularly effective in chronic carriers who have failed penicillin treatment 2

Alternative macrolides (if clindamycin cannot be used):

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 2, 1, 4
• Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg per dose) for 10 days 2
• Erythromycin: 20-40 mg/kg/day divided 2-3 times daily (maximum 1 gram per day) for 10 days 2

Critical Treatment Duration Requirements

A full 10-day course is essential for all antibiotics EXCEPT azithromycin to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever 2, 1

• Azithromycin requires only 5 days due to its prolonged tissue half-life 2, 1, 4
• Shortening the course by even a few days results in appreciable increases in treatment failure rates 2
• Therapy can be safely postponed up to 9 days after symptom onset and still prevent acute rheumatic fever 2

Important Resistance Considerations

Macrolide resistance:

• Approximately 5-8% resistance among Group A Streptococcus in the United States, varying geographically 2, 1
• Be aware of local resistance patterns before prescribing azithromycin or clarithromycin 2
• Approximately 1% of azithromycin-susceptible isolates become resistant following therapy 4

Clindamycin resistance:

• Remains very low at approximately 1% in the United States 2

Adjunctive Therapy

For symptom management:

• Acetaminophen or NSAIDs (such as ibuprofen) should be considered for moderate to severe symptoms or high fever 2, 1
• Avoid aspirin in children due to risk of Reye syndrome 2, 1
• Corticosteroids are NOT recommended as adjunctive therapy 2

Common Pitfalls to Avoid

Do not:

• Use cephalosporins in patients with immediate/anaphylactic penicillin reactions (10% cross-reactivity risk) 2, 1
• Prescribe shorter courses than recommended except for azithromycin's 5-day regimen 2, 1
• Use azithromycin as first-line therapy when penicillin can be used 2
• Use trimethoprim-sulfamethoxazole (Bactrim) for strep throat due to high resistance rates (50%) 2
• Assume all penicillin-allergic patients cannot receive cephalosporins—only those with immediate/anaphylactic reactions should avoid them 2

Special Populations

Chronic carriers:

• Generally do not require antimicrobial therapy, as they are unlikely to spread infection or develop complications 2, 1
• If treatment is indicated, clindamycin is particularly effective due to its ability to eradicate the organism 2, 1
• Routine post-treatment throat cultures are not recommended for asymptomatic patients who have completed therapy 2

Patients become non-contagious after 24 hours of antibiotic therapy 3