Diuretics: potassium-sparing: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · Diuretics: potassium-sparing

Sample item

A man with heart failure, already on an ACE inhibitor, is started on spironolactone. Two weeks later his potassium is 6.3 mmol/L, and he also notices breast tenderness. Which explanation is correct?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Spironolactone blocks aldosterone receptors in the collecting duct, reducing potassium secretion, and also blocks androgen receptors

Spironolactone is a competitive aldosterone antagonist acting on principal cells of the collecting duct, reducing sodium reabsorption and potassium secretion, so it can cause hyperkalaemia, especially with ACE inhibitors and renal impairment. Its antiandrogen and progestogen-like effects cause gynaecomastia and breast tenderness, which eplerenone largely avoids.

Option by option

  • A. Spironolactone inhibits the Na-K-2Cl cotransporter and causes potassium loss

    Loop diuretics inhibit NKCC2 and lose potassium.

  • B. Spironolactone stimulates the sodium-chloride cotransporter

    Thiazides inhibit the sodium-chloride cotransporter.

  • C. Spironolactone blocks aldosterone receptors in the collecting duct, reducing potassium secretion, and also blocks androgen receptors (correct)

    Correct. Aldosterone blockade causes hyperkalaemia and receptor cross-reactivity causes breast effects.

  • D. Spironolactone inhibits carbonic anhydrase and increases bicarbonate loss

    Acetazolamide inhibits carbonic anhydrase.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, Spironolactone blocks aldosterone receptors in the collecting duct, reducing potassium secretion, and also blocks androgen receptors. Spironolactone is a competitive aldosterone antagonist acting on principal cells of the collecting duct, reducing sodium reabsorption and potassium secretion, so it can cause hyperkalaemia, especially with ACE inhibitors and renal impairment.

Why is "Spironolactone inhibits the Na-K-2Cl cotransporter and causes potassi…" not the answer?

Loop diuretics inhibit NKCC2 and lose potassium.

Why is "Spironolactone stimulates the sodium-chloride cotransporter" not the answer?

Thiazides inhibit the sodium-chloride cotransporter.

Why is "Spironolactone inhibits carbonic anhydrase and increases bicarbonate…" not the answer?

Acetazolamide inhibits carbonic anhydrase.

What concept does this question test?

It tests Diuretics: potassium-sparing in Pharmacology. Its antiandrogen and progestogen-like effects cause gynaecomastia and breast tenderness, which eplerenone largely avoids.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Diuretics: potassium-sparing?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.