Hydrochlorothiazide should be used only in patients with what kind of renal function?

• A. It should not be used
• B. It is safe in renal failure
• C. Hydrochlorothiazide should be used only in patients with normal renal function
• D. It should be used in severe hepatic disease

Answer: (C)

Hydrochlorothiazide is a thiazide diuretic that blocks the Na+-Cl− cotransporter in the distal convoluted tubule, so its diuretic effect relies on delivering filtrate to that part of the nephron. If kidney function is impaired and GFR is low, there’s less filtrate reaching the distal tubule, making the drug less effective. Therefore it’s appropriate to use this drug mainly in patients with normal or near-normal renal function; in severe renal impairment, thiazides tend to be ineffective and loop diuretics are preferred. Hepatic disease isn’t the limiting factor here.