ACE inhibitors cough mechanism: The cough is primarily due to accumulation of which peptide?

• A. Angiotensin II
• B. Bradykinin
• C. Histamine
• D. Prostaglandin

Answer: (B)

The key idea is that ACE inhibitors provoke a cough because they raise levels of bradykinin. ACE normally breaks down bradykinin, so inhibiting ACE slows its degradation and allows bradykinin to accumulate. This buildup in the airways stimulates sensory nerves and promotes release of mediators like prostaglandins and nitric oxide, which irritate the cough reflex and produce a persistent dry cough seen with these drugs. Angiotensin II would actually decrease with ACE inhibition, not accumulate, so it isn’t the cause. Histamine is more associated with allergic reactions, and prostaglandins are downstream mediators rather than the primary trigger in this scenario.