What is the alternative treatment for a patient with streptococcal (strep) infection who is allergic to penicillin?

Alternative Treatments for Strep Throat in Penicillin-Allergic Patients

For patients with streptococcal (strep) throat infections who are allergic to penicillin, first-line alternatives include clindamycin, macrolides (erythromycin, clarithromycin, azithromycin), or first-generation cephalosporins (if no history of immediate hypersensitivity to penicillin). 1

Treatment Options Based on Type of Penicillin Allergy

For Patients with Severe/Immediate Penicillin Allergy (anaphylaxis, angioedema, urticaria)

• Clindamycin: 7 mg/kg per dose three times daily (maximum = 300 mg per dose) for 10 days 1, 2
• Macrolides:
  • Erythromycin: 20-40 mg/kg/day divided 2-3 times daily for 10 days 1
  • Clarithromycin: 7.5 mg/kg per dose twice daily (maximum = 250 mg per dose) for 10 days 1
  • Azithromycin: 12 mg/kg once daily (maximum = 500 mg) for 5 days 1, 3

For Patients with Non-Immediate/Non-Severe Penicillin Allergy

• First-generation cephalosporins (if no immediate hypersensitivity to penicillin):
  • Cephalexin (Keflex): 20 mg/kg per dose twice daily (maximum = 500 mg per dose) for 10 days 1
  • Cefadroxil: 30 mg/kg once daily (maximum = 1 g) for 10 days 1

Considerations for Antibiotic Selection

Efficacy and Evidence Quality

• First-generation cephalosporins have "strong, high" quality evidence for efficacy in penicillin-allergic patients without immediate hypersensitivity 1
• Clindamycin has "strong, moderate" quality evidence for efficacy 1
• Macrolides (azithromycin, clarithromycin) have "strong, moderate" quality evidence but carry concerns about resistance 1

Cross-Reactivity Concerns

• Cross-reactivity between penicillins and cephalosporins occurs in approximately 2% of cases, much lower than previously reported 8% 4
• Cephalosporins should be avoided in patients with history of immediate hypersensitivity reactions to penicillin (anaphylaxis, angioedema, urticaria) 1
• Macrolides and clindamycin have no cross-reactivity with penicillin and are safe options for patients with severe penicillin allergies 2, 5

Duration of Therapy

• Most oral antibiotics require a full 10-day course to achieve maximal pharyngeal eradication of group A streptococci 1, 6
• Azithromycin is the exception, requiring only a 5-day course due to its prolonged tissue half-life 1, 3, 7

Important Considerations and Pitfalls

Resistance Concerns

• Macrolide resistance among Group A Streptococcus varies geographically and temporally 1
• When using macrolides, be aware of potential QT interval prolongation, especially with erythromycin and clarithromycin 1
• Clindamycin resistance among Group A Streptococcus isolates in the United States is approximately 1% 1

Compliance Considerations

• Poor compliance with 10-day regimens is a major factor in treatment failures 8, 7
• Consider azithromycin's shorter 5-day course for patients with anticipated compliance issues 3, 7
• For patients unlikely to complete oral therapy, consider referral for parenteral options 1

Follow-up Recommendations

• Routine post-treatment throat cultures are not recommended for asymptomatic patients who have completed therapy 1, 6
• Consider follow-up testing only in special circumstances, such as patients with a history of rheumatic fever 1, 6

Remember that the full prescribed course of antibiotics must be completed even if symptoms resolve quickly to prevent complications such as rheumatic fever 1, 6.