Alpha blockers: phentolamine for vasopressor extravasation: 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 · Alpha blockers: phentolamine for vasopressor extravasation

Sample item

A patient on a peripheral intravenous noradrenaline infusion develops blanching, coolness and pain around the cannula site as the drug extravasates. Which agent infiltrated locally is the most appropriate antidote?

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

The answer and the reasoning

A. Phentolamine

Extravasated noradrenaline causes intense alpha-1 mediated vasoconstriction and risks tissue necrosis. Local infiltration of the non-selective alpha blocker phentolamine reverses the vasoconstriction and restores perfusion. Beta-blockers, antimuscarinics and cholinesterase inhibitors do not counter alpha-mediated ischaemia.

Option by option

  • A. Phentolamine (correct)

    Phentolamine is a competitive alpha antagonist that reverses the local vasoconstriction.

  • B. Atropine

    Atropine blocks muscarinic receptors and does not reverse catecholamine vasoconstriction.

  • C. Propranolol

    Propranolol blocks beta receptors and has no effect on alpha-1 vasoconstriction.

  • D. Neostigmine

    Neostigmine increases acetylcholine and is irrelevant to alpha-mediated ischaemia.

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 A, Phentolamine. Extravasated noradrenaline causes intense alpha-1 mediated vasoconstriction and risks tissue necrosis.

Why is "Atropine" not the answer?

Atropine blocks muscarinic receptors and does not reverse catecholamine vasoconstriction.

Why is "Propranolol" not the answer?

Propranolol blocks beta receptors and has no effect on alpha-1 vasoconstriction.

Why is "Neostigmine" not the answer?

Neostigmine increases acetylcholine and is irrelevant to alpha-mediated ischaemia.

What concept does this question test?

It tests Alpha blockers: phentolamine for vasopressor extravasation in Pharmacology. Local infiltration of the non-selective alpha blocker phentolamine reverses the vasoconstriction and restores perfusion. Beta-blockers, antimuscarinics and cholinesterase inhibitors do not counter alpha-mediated ischaemia.

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 Alpha blockers: phentolamine for vasopressor extravasation?

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.