Which mineral is associated with Lasix (furosemide), HCTZ (hydrochlorothiazide), and spironolactone?

• A. Potassium
• B. Calcium
• C. Magnesium
• D. Phosphorus

Answer: (A)

Potassium balance is the key idea here. Furosemide (a loop diuretic) increases potassium loss in the distal nephron, and hydrochlorothiazide (a thiazide) also promotes potassium excretion, both raising the risk of hypokalemia. Spironolactone (a potassium-sparing diuretic) blocks aldosterone in the collecting ducts, reducing potassium excretion and potentially raising potassium levels. Because these drugs collectively influence potassium handling in opposite directions, potassium is the mineral most closely linked to their effects. In clinical practice, monitoring potassium is crucial to prevent symptoms like weakness or dangerous heart rhythm changes in older adults. Calcium, magnesium, and phosphorus are affected by diuretics in different ways, but potassium is the common thread here.