What is the recommended treatment for a 12‑year‑old child weighing 149 lb (≈68 kg) with presumed streptococcal pharyngitis?

Treatment for Streptococcal Pharyngitis in a 12-Year-Old, 149 lb Patient

For this 12-year-old weighing 68 kg with presumed streptococcal pharyngitis, prescribe oral amoxicillin 1000 mg once daily (or 500 mg twice daily) for a full 10 days after confirming Group A Streptococcus infection with rapid antigen detection testing or throat culture. 1

Diagnostic Confirmation Required First

• Do not prescribe antibiotics empirically—confirm Group A Streptococcus (GAS) infection with either a rapid antigen detection test or throat culture before initiating treatment, as clinical features alone cannot reliably distinguish bacterial from viral pharyngitis. 1
• Testing is not recommended if clinical features strongly suggest viral etiology (cough, rhinorrhea, hoarseness, oral ulcers). 1
• A positive rapid antigen test is diagnostic and sufficient to begin treatment; backup culture is not needed in this age group unless the rapid test is negative. 1

First-Line Antibiotic Regimen

Amoxicillin is the drug of choice due to its proven efficacy, narrow spectrum, excellent safety profile, low cost, and the complete absence of documented penicillin resistance in GAS worldwide. 1

Specific Dosing for This Patient:

• Amoxicillin 1000 mg orally once daily for 10 days (preferred for adherence) 1, 2
• Alternative: Amoxicillin 500 mg orally twice daily for 10 days (equally effective) 1, 2
• At 68 kg, this patient exceeds 40 kg, so adult dosing applies rather than weight-based pediatric dosing. 2

Critical Treatment Duration:

• The full 10-day course is mandatory to achieve maximal pharyngeal eradication of GAS and prevent acute rheumatic fever, even if symptoms resolve within 3–4 days. 1, 2
• Shortening the course by even a few days results in appreciable increases in treatment failure rates and rheumatic fever risk. 1

Alternative Regimens for Penicillin Allergy

For Non-Immediate (Delayed) Penicillin Allergy:

First-generation cephalosporins are preferred with strong, high-quality evidence and only 0.1% cross-reactivity risk in patients with non-severe, delayed reactions. 1, 3

• Cephalexin 500 mg orally twice daily for 10 days 1
• Cefadroxil 1 gram orally once daily for 10 days 1

For Immediate/Anaphylactic Penicillin Allergy:

Avoid all beta-lactams (including cephalosporins) due to up to 10% cross-reactivity risk in patients with anaphylaxis, angioedema, or urticaria occurring within 1 hour of penicillin exposure. 1, 3

Clindamycin is the preferred alternative:

• Clindamycin 300 mg orally three times daily for 10 days 1, 3
• Clindamycin has only ~1% resistance among GAS in the United States and demonstrates superior eradication rates even in chronic carriers. 1, 3

Macrolide alternatives (less preferred due to resistance):

• Azithromycin 500 mg orally once daily for 5 days (only antibiotic requiring just 5 days due to prolonged tissue half-life) 1
• Clarithromycin 250 mg orally twice daily for 10 days 1
• Macrolide resistance in the United States is 5–8% and varies geographically, making these less reliable than clindamycin. 1, 3

Adjunctive Symptomatic Treatment

• Offer acetaminophen or ibuprofen for moderate to severe sore throat, fever, or systemic discomfort. 1
• Avoid aspirin in this 12-year-old due to Reye syndrome risk. 1
• Corticosteroids are not recommended as adjunctive therapy. 1

Common Pitfalls to Avoid

• Do not prescribe antibiotics without confirming GAS infection—viral pharyngitis accounts for 70–85% of acute pharyngitis cases and does not benefit from antibiotics. 1
• Do not shorten the antibiotic course below 10 days (except azithromycin's 5-day regimen)—this dramatically increases treatment failure and rheumatic fever risk. 1, 2
• Do not use trimethoprim-sulfamethoxazole (Bactrim)—it fails to eradicate GAS in 20–25% of cases and is not recommended. 3
• Do not order routine post-treatment throat cultures for asymptomatic patients who have completed therapy; reserve testing for special circumstances such as history of rheumatic fever. 1

Expected Clinical Course

• Symptoms typically resolve within 3–4 days without treatment, but antibiotics shorten symptom duration to less than 24 hours in most cases. 4
• Early treatment decreases suppurative complications, limits disease spread, and permits earlier return to school. 4
• The primary goal is preventing acute rheumatic fever and suppurative complications, not just symptom relief. 1