Which statement about hydrochlorothiazide is correct?

• A. It is a loop diuretic used to treat edema
• B. It increases potassium loss in urine
• C. It is a thiazide diuretic used to treat hypertension and peripheral edema
• D. It should be used only in patients with severe renal failure

Answer: (C)

Hydrochlorothiazide is a thiazide diuretic that works by inhibiting the Na+-Cl- cotransporter in the distal tubule, leading to increased excretion of sodium and water and, due to increased delivery of sodium to the collecting ducts, some potassium loss. This mechanism makes it effective for lowering blood pressure and treating peripheral edema.

The statement identifying it as a thiazide diuretic used to treat hypertension and peripheral edema best captures its primary clinical use. It is not a loop diuretic (those act in the loop of Henle, e.g., furosemide). It also isn’t best used only in severe renal failure; thiazides are less effective when kidney function is markedly reduced (low GFR), so their role is limited there. While they do cause potassium loss, that detail is not the defining use; the key point is its classification and typical indications.