Which medication, if taken with an ACE inhibitor, increases the risk of hyperkalemia?

• A. Colace
• B. Lasix
• C. Morphine
• D. Spironolactone

Answer: (D)

When a drug that affects aldosterone is added to an ACE inhibitor, the risk of high potassium rises. Spironolactone is a potassium-sparing diuretic that blocks aldosterone’s action in the distal nephron, so less potassium is excreted. An ACE inhibitor already lowers aldosterone production; combining it with spironolactone therefore markedly reduces potassium loss and can elevate serum potassium, leading to hyperkalemia. Clinically, this means monitoring potassium and kidney function, watching for symptoms like muscle weakness or irregular heartbeats, and avoiding high-potassium foods or salt substitutes.

Other options don’t raise this risk with an ACE inhibitor: a stool-softening agent has no electrolyte effect; a loop diuretic like furosemide increases potassium excretion; and morphine has no direct impact on potassium homeostasis.