A patient started on enalapril develops a persistent dry cough within two weeks. The mediator most responsible for this adverse effect is:

• A Reduced prostaglandin E2 synthesis
• B Increased angiotensin II acting on C-fibers
• C Direct irritation of the tracheal mucosa by the drug
• D Accumulation of bradykinin and substance P in the respiratory tract due to kininase II inhibition ✓

Explanation

ACE is identical to kininase II, the enzyme that degrades bradykinin and substance P. Inhibition allows these peptides to accumulate in the respiratory tract, provoking cough through sensory C-fiber stimulation. Angiotensin II levels fall rather than rise with ACE inhibitors, which eliminates option B, and switching to an ARB usually resolves the cough because ARBs do not affect kinin metabolism.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.