Question

Consider the following:
1. Metolazone
2. Amiloride
3. Triamterene
4. Chlorthalidone
Which of these are the potassium sparing diuretics?

• A. 1, 2 and 3
• B. 1, 2 and 4
• C. 2 and 3
• D. 1, 3 and 4

Hint:

Amiloride and triamterene block sodium channels in the collecting duct.

Answer 1

The Correct Option is C

Step 1: Understanding the Question.
We need to pick out which drugs from this list keep potassium in the body instead of wasting it in the urine.

Step 2: Key Concept.
Diuretics are grouped by where and how they act in the kidney tubule. Thiazide and thiazide-like diuretics act on the distal convoluted tubule and cause potassium loss, while potassium sparing diuretics act on the collecting duct and either block aldosterone or block sodium channels, which lets potassium stay in the body.

Step 3: Detailed Explanation.
Metolazone is a thiazide-like diuretic, and like other thiazides it increases potassium loss in the urine, so it is not potassium sparing. Amiloride blocks the epithelial sodium channel in the collecting duct, which reduces sodium reabsorption without pulling potassium out, making it a classic potassium sparing diuretic. Triamterene works by the same sodium channel blocking mechanism as amiloride and is grouped with it as a potassium sparing diuretic. Chlorthalidone is also a thiazide-like diuretic, closely related to hydrochlorothiazide in its action, and it too causes potassium loss rather than sparing it.

Step 4: Final Answer.
Amiloride and Triamterene are the potassium sparing diuretics in this list, so statements 2 and 3 are correct.