A 24-year-old man has resistant hypertension (BP 168/104 mmHg) with hypokalaemia (K 2.7 mEq/L) and metabolic alkalosis. Plasma renin activity is suppressed and plasma aldosterone is low. His father required early treatment for severe hypertension. Spironolactone produced only partial blood pressure control. Which drug is the definitive treatment?
- A Hydrochlorothiazide
- B Amiloride ✓
- C Eplerenone at higher dose
- D Captopril
Correct answer: B. Amiloride
Explanation
Low-renin, low-aldosterone hypertension with hypokalaemic alkalosis and autosomal dominant inheritance defines Liddle syndrome, caused by gain-of-function mutation of ENaC leading to unregulated sodium reabsorption and potassium secretion. Because aldosterone is not involved, mineralocorticoid receptor antagonists such as spironolactone and eplerenone fail. Amiloride or triamterene block ENaC directly and are the definitive therapy. Thiazides would worsen hypokalaemia, and ACE inhibition is ineffective because renin is already suppressed.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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