Pharmacology · single question
A penicillin-allergic patient is prescribed cephalexin and 30 minutes later becomes short of breath. Which molecule is primarily responsible?
Show answer and explanation
Correct answer: A. Histamine
- A. Correct. Cross-reactivity between penicillins and first-generation cephalosporins triggers IgE-mediated mast cell degranulation. Histamine release causes bronchoconstriction, vasodilation and increased vascular permeability within minutes.
- B. Interferon-gamma is a T-cell cytokine involved in delayed, cell-mediated responses.
- C. Bradykinin mediates ACE-inhibitor angioedema, which is not IgE-mediated and typically has a slower onset.
- D. Prostaglandins mediate inflammation and pain but are not the primary mediator of acute anaphylaxis.