A 55-year-old woman with hypertension and chronic kidney disease has a creatinine clearance of 22 mL/min. Her blood pressure remains uncontrolled on maximal tolerated doses of two agents. Which diuretic should be selected for add-on therapy?
- A Hydrochlorothiazide
- B Furosemide ✓
- C Chlorthalidone
- D Amiloride
Correct answer: B. Furosemide
Explanation
Thiazides act mainly on the distal convoluted tubule and lose antihypertensive and natriuretic efficacy when creatinine clearance falls below about 30 mL/min, so options A and C fail here. Loop diuretics act on the thick ascending limb where secretion into the tubular lumen persists in advanced renal failure, making furosemide effective, though larger doses may be required. Amiloride is potassium sparing and risks fatal hyperkalemia in CKD, so it is inappropriate.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
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