A 22-year-old man has hypertension (BP 158/98 mmHg), serum potassium of 2.9 mEq/L, metabolic alkalosis, plasma renin activity undetectable, and aldosterone level of 1 ng/dL. His father had similar untreated hypertension. Echocardiography is normal. Which drug will correct BOTH his hypertension and hypokalaemia?
- A Spironolactone
- B Amiloride ✓
- C Hydrochlorothiazide
- D Captopril
Correct answer: B. Amiloride
Explanation
Liddle syndrome is a gain-of-function mutation of the epithelial sodium channel (ENaC, SCNN1B or SCNN1G) causing excessive sodium reabsorption with potassium wasting, giving low renin and low aldosterone pseudoaldosteronism inherited in autosomal dominant fashion. Amiloride blocks ENaC directly and corrects both problems. Spironolactone fails because mineralocorticoid receptors are not involved, and ACE inhibition is useless when renin and angiotensin II are already suppressed.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.