Red man syndrome is most commonly associated with which antibiotic?

• A. Vancomycin
• B. Penicillin
• C. Ciprofloxacin
• D. Aztreonam

Answer: (A)

Red man syndrome is an infusion-related reaction caused by rapid IV vancomycin, due to histamine release from mast cells. It presents as flushing and pruritus of the face, neck, and upper body, and can be accompanied by a diffuse rash and sometimes low blood pressure. It’s not a true IgE-mediated allergy; slowing or stopping the infusion and giving an antihistamine typically resolves the symptoms.

Among the antibiotics listed, vancomycin is the classic cause of this reaction. The other drugs—penicillin, ciprofloxacin, and aztreonam—do not classically produce red man syndrome through this mechanism, though they can cause other types of allergic or adverse reactions.