What is the recommended antibiotic regimen, dosage, and duration for a 7-year-old, 70‑lb child with a positive rapid strep test for group A Streptococcus?

Recommended Antibiotic Regimen for a 70-Pound, 7-Year-Old with Positive Rapid Strep Test

Prescribe oral amoxicillin 750 mg (25 mg/kg) twice daily for a full 10 days to this 32-kg child with confirmed Group A streptococcal pharyngitis. 1, 2, 3

Dosing Calculation and Rationale

• Weight-based dosing: This 70-pound (31.8 kg) child should receive 25 mg/kg twice daily, which equals approximately 750–800 mg per dose (maximum 1000 mg per dose). 1, 2, 3
• Amoxicillin is the first-line agent because of its proven efficacy, narrow spectrum, excellent safety profile, low cost, and superior palatability compared to penicillin V in young children. 1, 2, 4
• No documented penicillin resistance exists worldwide among Group A Streptococcus, guaranteeing reliable bacterial eradication. 1, 2
• Twice-daily dosing improves adherence compared to penicillin V's three- or four-times-daily regimen, while maintaining identical efficacy. 4, 5

Critical Treatment Duration

• A complete 10-day course is mandatory to achieve maximal pharyngeal eradication of Group A Streptococcus and to prevent acute rheumatic fever. 1, 2, 4, 5
• Shortening the course by even a few days dramatically increases treatment-failure rates and the risk of acute rheumatic fever, even if symptoms resolve within 3–4 days. 1, 2, 5
• The primary goal is preventing acute rheumatic fever and suppurative complications, not just symptom relief; this requires complete bacterial eradication. 1, 2

Alternative Regimens (If Amoxicillin Cannot Be Used)

For Non-Immediate (Delayed) Penicillin Allergy

• First-generation cephalosporins are preferred: cephalexin 20 mg/kg per dose (approximately 640 mg) twice daily for 10 days (maximum 500 mg per dose). 1, 2
• Cross-reactivity risk is only 0.1% in patients with delayed, mild penicillin reactions such as a rash occurring more than 1 hour after exposure. 1, 2

For Immediate/Anaphylactic Penicillin Allergy

• Clindamycin is the preferred choice: 7 mg/kg per dose (approximately 220 mg) three times daily for 10 days (maximum 300 mg per dose). 1, 2
• Clindamycin resistance is only ~1% among U.S. Group A Streptococcus isolates and demonstrates superior eradication even in chronic carriers. 1, 2
• Azithromycin is an acceptable alternative: 12 mg/kg once daily (approximately 380 mg) for 5 days (maximum 500 mg), but macrolide resistance ranges from 5–8% in the United States. 1, 2, 6
• Clarithromycin is another option: 7.5 mg/kg per dose (approximately 240 mg) twice daily for 10 days (maximum 250 mg per dose), with similar resistance concerns as azithromycin. 1, 2

Adjunctive Symptomatic Care

• Offer acetaminophen or ibuprofen for moderate-to-severe sore throat, fever, or systemic discomfort. 1, 2
• Avoid aspirin in children due to the risk of Reye syndrome. 1, 2
• Corticosteroids are not recommended as adjunctive therapy for streptococcal pharyngitis. 1, 2

Common Pitfalls to Avoid

• Do not prescribe less than 10 days (except azithromycin's 5-day regimen) because this markedly increases treatment failure and rheumatic-fever risk. 1, 2, 5
• Do not use cephalosporins in patients with immediate/anaphylactic penicillin reactions due to the ~10% cross-reactivity risk with all beta-lactam antibiotics. 1, 2
• Do not order routine post-treatment throat cultures for asymptomatic patients who have completed therapy; reserve testing for special circumstances such as a history of rheumatic fever. 1, 2
• Do not use trimethoprim-sulfamethoxazole (Bactrim) because sulfonamides fail to eradicate Group A Streptococcus in 20–25% of cases. 2

Monitoring and Follow-Up

• Reassess the patient within 48–72 hours if there is no clinical improvement, as this may indicate non-compliance, an alternative diagnosis, or a suppurative complication. 2
• Emphasize completing the entire 10-day regimen to parents, even when the child feels better after 2–3 days, to prevent acute rheumatic fever. 1, 2, 5