What is the best treatment for a 9-year-old child with streptococcal (strep) pharyngitis who is intolerant to amoxicillin?

Treatment for 9-Year-Old with Strep Pharyngitis and Amoxicillin Intolerance

For a 9-year-old with confirmed strep throat and amoxicillin intolerance, prescribe cephalexin 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days if the intolerance is non-anaphylactic, or clindamycin 7 mg/kg per dose three times daily (maximum 300 mg/dose) for 10 days if the reaction was immediate or anaphylactic. 1, 2

Critical First Step: Determine the Type of Reaction

You must distinguish between non-anaphylactic intolerance and immediate/anaphylactic allergy before selecting an antibiotic. 2

• Non-anaphylactic reactions include delayed rash (appearing >1 hour after administration), mild gastrointestinal upset, or non-urticarial skin reactions. 2
• Immediate/anaphylactic reactions include anaphylaxis, angioedema, respiratory distress, urticaria, or bronchospasm occurring within 1 hour of amoxicillin administration. 2

Treatment Algorithm Based on Reaction Type

For Non-Anaphylactic Amoxicillin Intolerance

First-generation cephalosporins are the preferred choice with strong, high-quality evidence. 1, 2, 3

• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days 1, 2
• Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days 1, 2

Why first-generation cephalosporins?

• Cross-reactivity risk is only 0.1% in patients with non-severe, delayed penicillin reactions 2
• Strong, high-quality evidence supports their efficacy 1, 2
• Narrow spectrum minimizes disruption to normal flora 3
• Proven efficacy, low cost, and excellent safety profile 1, 2

For Immediate/Anaphylactic Amoxicillin Allergy

Clindamycin is the preferred choice with strong, moderate-quality evidence. 1, 2

• Clindamycin: 7 mg/kg per dose three times daily (maximum 300 mg/dose) for 10 days 1, 2

Why clindamycin over macrolides?

• Only ~1% resistance rate among Group A Streptococcus in the United States 2
• Macrolide resistance is 5-8% and varies geographically 1, 2
• Demonstrates high efficacy even in chronic carriers and treatment failures 2
• All beta-lactams must be avoided due to up to 10% cross-reactivity risk with cephalosporins in immediate hypersensitivity 1, 2

Alternative if clindamycin cannot be used:

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 2, 4
• Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg/dose) for 10 days 1, 2

Critical Treatment Duration Requirements

A full 10-day course is mandatory for all antibiotics except azithromycin to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever. 1, 2, 3, 5

• Azithromycin requires only 5 days due to its prolonged tissue half-life 1, 2, 4
• Shortening the course below 10 days dramatically increases treatment failure rates and rheumatic fever risk 2, 5
• Even though symptoms typically resolve within 3-4 days, full course completion is essential for preventing complications 2, 5

Common Pitfalls to Avoid

• Do not use cephalosporins if the patient had anaphylaxis, angioedema, or immediate urticaria to amoxicillin due to 10% cross-reactivity risk 1, 2
• Do not prescribe azithromycin as first-line therapy when cephalosporins or clindamycin can be used—reserve it for documented penicillin allergy with contraindications to other alternatives 2
• Do not shorten the antibiotic course below 10 days (except azithromycin's 5-day regimen) even if symptoms improve 2, 5
• Do not prescribe broad-spectrum cephalosporins (cefdinir, cefpodoxime) when narrow-spectrum first-generation agents are appropriate 2

Adjunctive Symptomatic Treatment

• Acetaminophen or ibuprofen for moderate to severe symptoms or high fever 1, 2, 3, 5
• Avoid aspirin in children due to Reye syndrome risk 1, 2, 3, 5
• Corticosteroids are not recommended 2, 3

Special Considerations for Macrolides

If azithromycin or clarithromycin must be used:

• Be aware that macrolide resistance varies geographically (5-8% in the United States) 1, 2
• Azithromycin was clinically and microbiologically superior to penicillin V at Days 14 and 30 in U.S. studies, with 95% bacteriologic eradication at Day 14 4
• However, some studies show azithromycin 10 mg/kg for 3 days had inferior bacteriologic eradication compared to penicillin (65% vs. 82%) 6
• The optimal azithromycin regimen is 12 mg/kg once daily for 5 days (total dose 60 mg/kg), which provides the best eradication rates 7, 4