Pharmacology · single question
A patient with a penicillin allergy presents for tooth extraction. You note they are also allergic to cephalexin. Which antibiotic is the MOST appropriate alternative for endocarditis prophylaxis?
Show answer and explanation
Correct answer: A. Azithromycin 500mg
Azithromycin 500mg (or clarithromycin 500mg, or doxycycline 100mg) is the appropriate alternative for penicillin-allergic patients who ALSO cannot take cephalosporins (cross-reactive allergy or anaphylaxis history). Per the 2021 AHA Scientific Statement: clindamycin is NO LONGER recommended due to C. difficile risk. For those allergic to penicillin AND unable to take cephalosporins, macrolides (azithromycin, clarithromycin) or doxycycline are used.
- A. ✅ CORRECT – Azithromycin 500mg (or clarithromycin 500mg, doxycycline 100mg) for penicillin-allergic patients who also cannot take cephalosporins.
- B. ❌ Amoxicillin is a penicillin — contraindicated in penicillin-allergic patients.
- C. ❌ Cefazolin is a cephalosporin — contraindicated if the patient also has a cephalosporin allergy.
- D. ❌ Clindamycin was removed from the 2021 AHA endocarditis prophylaxis guidelines due to unacceptable risk of C. difficile.