What is the recommended treatment for strep throat in a patient with a penicillin allergy?

Treatment of Strep Throat in Penicillin-Allergic Patients

For patients with non-immediate (non-anaphylactic) penicillin allergy, first-generation cephalosporins like cephalexin or cefadroxil are the preferred first-line alternatives, while patients with immediate/anaphylactic penicillin reactions should receive clindamycin as the preferred choice. 1

Determining the Type of Penicillin Allergy

The critical first step is distinguishing between immediate and non-immediate reactions, as this determines whether cephalosporins can be safely used 1:

• Immediate/anaphylactic reactions include anaphylaxis, angioedema, respiratory distress, or urticaria occurring within 1 hour of penicillin administration 1
• Non-immediate reactions include delayed rashes or other mild symptoms occurring after 1 hour 1
• Up to 10% of patients with immediate hypersensitivity to penicillin may have cross-reactivity with first-generation cephalosporins, making all beta-lactams unsafe in this group 1, 2

Treatment Algorithm for Non-Immediate Penicillin Allergy

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

• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days 1
• Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days 1
• Cross-reactivity risk is only 0.1% in patients with non-severe, delayed penicillin reactions 1

Treatment Algorithm for Immediate/Anaphylactic Penicillin Allergy

Clindamycin is the preferred alternative with strong, moderate-quality evidence 1:

• Dosing: 7 mg/kg per dose three times daily (maximum 300 mg/dose) for 10 days 1
• Clindamycin resistance among Group A Streptococcus in the United States is approximately 1%, making it highly reliable 1
• Clindamycin demonstrates high efficacy in eradicating streptococci, even in chronic carriers 1

Alternative Options for Immediate Allergy

If clindamycin cannot be used, macrolides are acceptable alternatives 1:

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 3

  • Only antibiotic requiring just 5 days due to prolonged tissue half-life 1
  • Macrolide resistance is 5-8% in the United States 1
  • FDA-approved specifically for pharyngitis/tonsillitis caused by Streptococcus pyogenes as an alternative to first-line therapy 3

• Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg/dose) for 10 days 1

  • Similar resistance concerns as azithromycin 1

• Erythromycin: 20-40 mg/kg/day divided 2-3 times daily (maximum 1 gram/day) for 10 days 1

  • Less preferred due to high rate of gastrointestinal side effects 1, 4

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 1, 2:

• Shortening the course by even a few days results in appreciable increases in treatment failure rates 1
• Azithromycin is the only exception, requiring 5 days due to its unique pharmacokinetics 1, 3
• The primary goal is not only symptomatic improvement but also prevention of acute rheumatic fever, which requires adequate bacterial eradication 1

Important Resistance Considerations

When selecting among alternatives for immediate allergy 1:

• Clindamycin: ~1% resistance in the United States, making it the most reliable option 1
• Macrolides (azithromycin/clarithromycin): 5-8% resistance in the United States, varies geographically 1
• Be aware of local resistance patterns when prescribing macrolides 1

Common Pitfalls to Avoid

• Do not use cephalosporins in patients with immediate/anaphylactic penicillin reactions due to the 10% cross-reactivity risk 1, 2
• Do not assume all penicillin-allergic patients cannot receive cephalosporins - only those with immediate reactions should avoid them 1, 2
• Do not prescribe shorter courses than recommended (except azithromycin's 5-day regimen) to prevent treatment failure and acute rheumatic fever 1, 2
• Do not use azithromycin as first-line therapy - it should be reserved for penicillin-allergic patients due to resistance concerns 1
• Do not use trimethoprim-sulfamethoxazole (Bactrim) for strep throat due to high resistance rates and lack of efficacy against Group A Streptococcus 1

Adjunctive Therapy

For symptom management 1:

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

Post-Treatment Considerations

• Routine follow-up throat cultures or rapid antigen detection tests are not recommended for asymptomatic patients who have completed therapy 1
• Testing should only be considered in special circumstances, such as patients with a history of rheumatic fever 1