A Patient who is on antihypertensive drug develops a dry cough. Which of the following drug might be responsible for the condition:
**Core Concept**
ACE inhibitors block the angiotensin-converting enzyme, preventing the conversion of angiotensin I to angiotensin II. This leads to vasodilation and reduced blood pressure. A well-known side effect of ACE inhibitors is a persistent dry cough, attributed to accumulation of bradykinin, which stimulates sensory nerves in the airways.
**Why the Correct Answer is Right**
ACE inhibitors inhibit the breakdown of bradykinin, leading to its accumulation in the lungs. Bradykinin stimulates cough receptors in the airways, resulting in a dry, non-productive cough. This adverse effect is one of the most common reasons for discontinuation of ACE inhibitors. The mechanism is distinct from other antihypertensives and is specifically linked to the bradykinin pathway.
**Why Each Wrong Option is Incorrect**
Option A: Diuretics do not cause dry cough; they primarily lead to electrolyte imbalances and volume depletion, not respiratory symptoms.
Option C: Calcium channel blockers reduce vascular resistance but do not affect bradykinin or airway sensitivity; they are rarely associated with cough.
Option D: Beta-blockers may cause fatigue or bradycardia but are not linked to dry cough as a side effect.
**Clinical Pearl / High-Yield Fact**
"ACE inhibitors cause dry cough due to bradykinin accumulation — if a patient develops a cough while on this drug, consider switching to an ARB (angiotensin receptor blocker), which avoids this issue."
✓ Correct Answer: B. ACE inhibitors