Which diuretic is specifically associated with hyperkalemia and hyponatremia in CrCl < 30?

• A. Spironolactone
• B. Amiloride
• C. Triamterene
• D. Eplerenone

Answer: (C)

The main point is that potassium-sparing diuretics that block the epithelial sodium channel (ENaC) in the distal nephron can cause both hyperkalemia and hyponatremia, especially when kidney function is severely reduced. Triamterene directly inhibits ENaC, decreasing sodium reabsorption and the lumen-negative potential that drives potassium secretion. In CrCl < 30, this reduced potassium excretion leads to hyperkalemia, while increased distal sodium loss can contribute to hyponatremia. Spironolactone and eplerenone raise potassium via mineralocorticoid receptor antagonism but are less commonly linked to hyponatremia; amiloride also blocks ENaC and can cause similar effects, but tri­amterene is the classic example associated with both electrolyte disturbances in advanced CKD.