A patient with a prosthetic heart valve is allergic to penicillin. No azithromycin, doxycycline, or cephalexin is available. What is the BEST prophylactic antibiotic?

Correct answer: D. Clarithromycin

• A. Incorrect. Metronidazole has NO role in endocarditis prophylaxis.
• B. Incorrect. Vancomycin IV is for hospitalized patients with severe allergy — not standard outpatient dental prophylaxis.
• C. Incorrect. Amoxicillin is a penicillin — contraindicated in this patient.
• D. Correct. Per AHA guidelines for endocarditis prophylaxis in penicillin-allergic patients who cannot take cephalosporins, options include clindamycin (now less preferred), azithromycin, or clarithromycin. Since azithromycin and cephalexin are excluded from options, clarithromycin is the best available choice.