Correct Answer: B. Lisinopril
Lisinopril, an ACE inhibitor, is the most likely culprit in this clinical presentation. ACE inhibitors are notorious for causing a persistent dry cough that occurs in 5–10% of patients within weeks to months of initiation. The mechanism is well-established: ACE inhibitors block the conversion of angiotensin I to angiotensin II, but more importantly, they prevent the degradation of bradykinin by ACE (kininase II). Accumulated bradykinin stimulates C-fibers in the airways, triggering a characteristic dry, non-productive cough that is often worse at night or when lying down. This cough is not dose-dependent and does not resolve with continued therapy in most patients. It is a class effect of all ACE inhibitors (enalapril, ramipril, captopril, lisinopril) and is one of the most common reasons for drug discontinuation in Indian clinical practice. The cough typically resolves within 1–4 weeks of stopping the drug. While the question stem mentions "the following picture," the clinical presentation described is consistent with ACE inhibitor–induced cough, making lisinopril the correct answer among the given options.
Why the other options are wrong
A. Clonidine LA — Clonidine, a central α₂-agonist, causes dry mouth, sedation, and rebound hypertension upon withdrawal—not a persistent cough. While clonidine can cause bronchospasm in susceptible patients, it does not produce the characteristic bradykinin-mediated cough seen with ACE inhibitors. The NBE trap here is pairing clonidine with 'dry' symptoms to confuse students. C. Nifedipine — Nifedipine, a dihydropyridine calcium channel blocker, causes reflex tachycardia, flushing, headache, and peripheral edema—not cough. While nifedipine can worsen heart failure or cause palpitations, it does not trigger the bradykinin-mediated airway irritation that produces ACE inhibitor cough. This is a classic distractor for CVS drug side effects. D. Atenolol — Atenolol, a β₁-selective blocker, causes fatigue, bradycardia, and bronchospasm (especially in asthmatics)—not a dry cough. Although β-blockers can worsen asthma or COPD through airway constriction, they do not produce the persistent, non-productive cough characteristic of ACE inhibitor use. The NBE may pair β-blockers with respiratory symptoms to mislead.
High-Yield Facts
- ACE inhibitor cough occurs in 5–10% of patients, is non-productive and dry, and is mediated by bradykinin accumulation, not angiotensin II blockade.
- Mechanism: ACE (kininase II) normally degrades bradykinin; inhibition → C-fiber stimulation in airways → cough reflex.
- Class effect: All ACE inhibitors (lisinopril, enalapril, ramipril, captopril) cause cough; ARBs do NOT because they do not block bradykinin degradation.
- Management: Cough resolves within 1–4 weeks of drug discontinuation; switching to an ARB (losartan, valsartan) is the standard Indian DOC alternative.
- Not dose-dependent and does not improve with continued therapy; patient education and early recognition are critical in Indian outpatient settings.
Mnemonics
ACE Cough = Bradykinin ACE inhibitors → Cough via Excessive Bradykinin. Remember: ACE blocks angiotensin AND bradykinin breakdown → cough, not BP drop alone. ARB No Cough Angiotensin Receptor Blockers block the receptor downstream, so bradykinin still gets degraded → no cough. Use this to switch patients.
NBE Trap
NBE pairs ACE inhibitors with "dry" symptoms and may include clonidine (also causes dryness) as a distractor. The key discriminator is that ACE cough is persistent and non-productive, while clonidine causes dry mouth and sedation—different organ systems, different mechanisms.
Clinical Pearl
In Indian primary care, ACE inhibitor–induced cough is one of the top reasons for antihypertensive non-adherence. Early recognition and switching to an ARB (losartan, valsartan) or other class (calcium channel blocker, thiazide) prevents patient dropout and improves BP control in the long term.
_Reference: KD Tripathi Ch. 21 (ACE Inhibitors); Harrison Ch. 246 (Hypertension Management)_