What is a pharmacologic rationale for adding a potassium-sparing diuretic to antihypertensive therapy?

• A. To increase potassium loss
• B. To conserve potassium
• C. To reduce diuretic efficacy
• D. To decrease antihypertensive efficacy

Answer: (B)

The key idea is to conserve potassium when using diuretics for high blood pressure. Thiazide and loop diuretics promote potassium loss in the distal nephron, which can lead to hypokalemia and related complications. Adding a potassium-sparing diuretic counteracts this by reducing potassium excretion in the collecting ducts. Some potassium-sparing agents block aldosterone, while others block sodium channels in the distal tubule, both actions helping to keep potassium levels normal while still promoting diuresis and lowering blood pressure. This approach improves safety by preventing potassium depletion, though it requires monitoring for potential hyperkalemia, especially if the patient is also taking ACE inhibitors, ARBs, or potassium supplements.