## Most Common Cause of Drug-Induced Cough in Antihypertensives ### Mechanism of ACE Inhibitor-Induced Cough **Key Point:** ACE inhibitors cause a persistent dry cough in 5–10% of patients due to inhibition of bradykinin degradation in the lungs. 1. ACE (angiotensin-converting enzyme) normally degrades **bradykinin** in pulmonary tissue. 2. ACE inhibition → ↑ bradykinin accumulation → stimulation of C-fibers in airways → cough reflex. 3. Cough typically appears within **weeks to months** of initiation. 4. Resolves **within 1–4 weeks** of drug discontinuation. ### Why ACE Inhibitors Are the Culprit **High-Yield:** ACE inhibitor–induced cough is one of the most frequent reasons for drug discontinuation in hypertension management, affecting up to 1 in 10 patients. | Feature | ACE Inhibitor | ARB | Beta-blocker | CCB | |---------|---------------|-----|--------------|-----| | Bradykinin ↑ | Yes | No | No | No | | Cough incidence | 5–10% | <1% | Rare | Rare | | Onset | Weeks–months | — | — | — | | Reversibility | Yes (1–4 weeks) | — | — | — | ### Clinical Pearl **Clinical Pearl:** Patients who develop ACE inhibitor cough can often be switched to an ARB (which blocks the AT1 receptor downstream, bypassing bradykinin accumulation) without recurrence of cough. ### Management 1. **Confirm diagnosis:** Temporal relationship to ACE inhibitor initiation and resolution after discontinuation. 2. **Switch therapy:** ARB is the preferred alternative (same BP control, no cough). 3. **Rarely:** Cough suppressants (e.g., codeine) are not effective and are not recommended as first-line management. **Tip:** In NEET PG exams, if a question mentions "dry cough + antihypertensive," the answer is almost always **ACE inhibitor** unless the stem explicitly states ARB or another class.
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