Azithromycin (Z-pak) for Strep Throat in a Patient Allergic to Amoxicillin and Clarithromycin
Azithromycin (Z-pak) is an appropriate alternative treatment for streptococcal infection in a patient with allergies to both amoxicillin and clarithromycin. 1, 2
Rationale for Using Azithromycin
Azithromycin is indicated for the treatment of pharyngitis/tonsillitis caused by Streptococcus pyogenes as an alternative to first-line therapy in individuals who cannot use first-line therapy 1. While penicillin is typically the drug of choice for streptococcal infections, patients with allergies require alternative options.
Safety in Patients with Penicillin Allergy
- Research has demonstrated that azithromycin is safe in patients with allergies to penicillin and cephalosporins 3
- There is no cross-reactivity between macrolides (like azithromycin) and beta-lactams (like amoxicillin) due to their different chemical structures
Effectiveness Against Streptococcal Infections
- Azithromycin has demonstrated efficacy in eradicating Streptococcus pyogenes in clinical studies 4, 5
- The bacteriological eradication rate for azithromycin in streptococcal pharyngitis has been shown to be approximately 94-96% 4
Dosing Considerations
For streptococcal pharyngitis/tonsillitis in adults:
- Standard Z-pak dosing: 500 mg on day 1, followed by 250 mg daily for 4 days (total 5-day course)
- This shorter course is possible due to azithromycin's prolonged tissue half-life 6
Important Precautions
Potential Side Effects
- Gastrointestinal effects: nausea, diarrhea, abdominal pain
- Rare but serious: QT prolongation, hepatotoxicity, Clostridium difficile-associated diarrhea 1
- Monitor for signs of allergic reaction, though cross-reactivity with penicillin allergy is not expected
Resistance Considerations
- Macrolide resistance is increasing, with approximately 40% resistance for S. pneumoniae in the US 2
- However, for Group A Streptococcal infections, azithromycin remains an effective alternative when penicillin cannot be used
Follow-up Recommendations
- Patient should complete the full course of antibiotics even if symptoms improve
- If no improvement is seen within 48-72 hours, reevaluation is necessary 2
- Consider throat culture if treatment fails to ensure the infection is responding
Alternative Options
If azithromycin is contraindicated or unavailable:
- Clindamycin (300-450 mg orally three times daily for 10 days) is another alternative for patients with penicillin allergy 2, 7
- Doxycycline may be considered in adult patients (not pregnant women or children) 2
Special Considerations
- Penicillin remains the gold standard for preventing rheumatic fever, a potential complication of streptococcal infections 1, 6
- While azithromycin is effective for symptom relief and bacterial eradication, data establishing efficacy in preventing rheumatic fever are not available 1
Azithromycin (Z-pak) provides a convenient, effective, and well-tolerated treatment option for streptococcal pharyngitis in patients with allergies to both amoxicillin and clarithromycin.