A 55-year-old hypertensive man on enalapril develops recurrent episodes of non-pruritic swelling of the lips and tongue. The attacks occur because the drug impairs degradation of a peptide mediator that increases vascular permeability and produces pain during inflammation. Which mediator is accumulating?

• A Bradykinin ✓
• B Substance P
• C Histamine
• D Prostaglandin E2

Explanation

Bradykinin, cleaved from high molecular weight kininogen by kallikrein, causes increased vascular permeability, smooth muscle contraction, and pain. It is degraded by angiotensin converting enzyme, so ACE inhibitors cause bradykinin accumulation and life-threatening angioedema. Histamine also raises permeability but produces itching through sensory nerve stimulation rather than the drug-related mechanism here, and its metabolism does not depend on ACE.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.