A 62-year-old man with hypertension on enalapril for 3 months develops a persistent dry cough and mild dyspnea. He denies fever, chest pain, or orthopnea. Chest X-ray is normal. His blood pressure is well-controlled at 128/82 mmHg. What is the most appropriate next step in management?

Question

Accepted Answer

D. Discontinue enalapril and switch to an ARB (losartan). ## Clinical Context
This patient presents with a classic **Type A (Augmented) Adverse Drug Reaction** — a dose-dependent, predictable side effect of ACE inhibitors caused by accumulation of bradykinin and substance P in the lungs.

## Mechanism of ACE Inhibitor-Induced Cough

**Key Point:** ACE inhibitors block conversion of angiotensin I to angiotensin II AND inhibit degradation of bradykinin and substance P. These inflammatory mediators accumulate in respiratory epithelium, triggering a dry, persistent cough in 5–10% of patients.

## Diagnostic Features
- Onset: typically 1–3 months after initiation (as in this case)
- Character: dry, non-productive, worse at night or when lying down
- Investigations: normal chest X-ray, normal spirometry (rules out organic lung disease)
- Resolution: occurs within 1–4 weeks of drug discontinuation

## Management Algorithm

```mermaid
flowchart TD
  A[ACE inhibitor-induced cough suspected]:::outcome --> B{Diagnosis confirmed?}:::decision
  B -->|Yes: normal CXR, typical timeline| C[Discontinue ACE inhibitor]:::action
  C --> D[Switch to ARB or alternative agent]:::action
  B -->|No: abnormal CXR, fever, crackles| E[Investigate for pneumonia, ILD]:::urgent
  D --> F[Cough resolves in 1-4 weeks]:::outcome
```

**High-Yield:** ARBs (losartan, valsartan) do NOT cause cough because they block the angiotensin II receptor downstream and do not affect bradykinin metabolism. They are the preferred alternative in ACE inhibitor-induced cough.

## Why Discontinuation + ARB Switch?

1. **Diagnosis is Type A (predictable, dose-related)** — not a rare idiosyncratic reaction
2. **Normal CXR excludes organic pathology** — no need for advanced imaging
3. **ARBs provide equivalent BP control without cough** — evidence-based alternative
4. **Cough suppressants are ineffective** — they do not address the underlying mechanism

**Clinical Pearl:** Some patients tolerate cough and choose to continue ACE inhibitors; however, switching to an ARB is the standard recommendation when cough is bothersome or affects quality of life.

[cite:KD Tripathi 8e Ch 26]

Answer

A. Add a calcium channel blocker and continue enalapril

Answer

B. Continue enalapril and add a cough suppressant

Answer

C. Perform high-resolution CT chest to rule out interstitial lung disease

A 62-year-old man with hypertension on enalapril for 3 months develops a persistent dry cough and mild dyspnea. He denies fever, chest pain, or orthopnea. Chest X-ray is normal. His blood pressure is well-controlled at 128/82 mmHg. What is the most appropriate next step in management?

Explanation

Clinical Context

Mechanism of ACE Inhibitor-Induced Cough

Diagnostic Features

Management Algorithm

Why Discontinuation + ARB Switch?

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