Urology: nitrates and phosphodiesterase-5 inhibitors: practice question

A General Surgery 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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General Surgery · Urology: nitrates and phosphodiesterase-5 inhibitors

Sample item

A 62-year-old man with angina taking isosorbide mononitrate asks his surgeon for sildenafil for erectile dysfunction. Why is the combination contraindicated?

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

The answer and the reasoning

B. Both increase cGMP-mediated vasodilatation and can cause profound hypotension

Nitrates release nitric oxide and sildenafil inhibits cGMP breakdown, so together they cause marked vasodilatation and life-threatening hypotension. Sildenafil must not be given within 24 hours of a nitrate. Alternatives include other treatments of erectile dysfunction.

Option by option

  • A. Nitrates impair absorption of sildenafil, making it ineffective

    Nitrates do not reduce the absorption of sildenafil.

  • B. Both increase cGMP-mediated vasodilatation and can cause profound hypotension (correct)

    Correct. The combined effect on cGMP produces severe hypotension.

  • C. Sildenafil causes coronary vasospasm that nitrates cannot relieve

    Sildenafil does not cause coronary vasospasm.

  • D. Sildenafil blocks hepatic metabolism of the nitrate, causing toxicity

    Sildenafil does not impair hepatic nitrate metabolism; the interaction is pharmacodynamic.

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 General Surgery question

What is the answer to this General Surgery question?

The best answer is B, Both increase cGMP-mediated vasodilatation and can cause profound hypotension. Nitrates release nitric oxide and sildenafil inhibits cGMP breakdown, so together they cause marked vasodilatation and life-threatening hypotension.

Why is "Nitrates impair absorption of sildenafil, making it ineffective" not the answer?

Nitrates do not reduce the absorption of sildenafil.

Why is "Sildenafil causes coronary vasospasm that nitrates cannot relieve" not the answer?

Sildenafil does not cause coronary vasospasm.

Why is "Sildenafil blocks hepatic metabolism of the nitrate, causing toxicity" not the answer?

Sildenafil does not impair hepatic nitrate metabolism; the interaction is pharmacodynamic.

What concept does this question test?

It tests Urology: nitrates and phosphodiesterase-5 inhibitors in General Surgery. Sildenafil must not be given within 24 hours of a nitrate. Alternatives include other treatments of erectile dysfunction.

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 Urology: nitrates and phosphodiesterase-5 inhibitors?

Learn classic signs and eponyms alongside what they diagnose. Then use the flashcards and the other General Surgery 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.