Autonomic nervous system: pheochromocytoma and beta-blockade: 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 · Autonomic nervous system: pheochromocytoma and beta-blockade

Sample item

A man with a catecholamine-secreting adrenal tumour is given propranolol alone to control a fast heart rate and develops a hypertensive crisis. What is the best explanation?

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

The answer and the reasoning

D. Unopposed alpha-mediated vasoconstriction

Beta-2 mediated vasodilation partly offsets the alpha-1 vasoconstriction caused by circulating catecholamines. Blocking beta receptors first leaves alpha effects unopposed and the pressure rises. Alpha blockade with phenoxybenzamine is started before any beta-blocker.

Option by option

  • A. Stimulation of muscarinic receptors

    Propranolol does not stimulate muscarinic receptors.

  • B. Reduced clearance of catecholamines

    Propranolol does not meaningfully slow the clearance of catecholamines.

  • C. Increased renin release by the drug

    Beta blockade reduces renin release, so this would lower rather than raise pressure.

  • D. Unopposed alpha-mediated vasoconstriction (correct)

    Correct. Without beta-2 vasodilation, alpha-1 vasoconstriction acts unopposed.

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 D, Unopposed alpha-mediated vasoconstriction. Beta-2 mediated vasodilation partly offsets the alpha-1 vasoconstriction caused by circulating catecholamines.

Why is "Stimulation of muscarinic receptors" not the answer?

Propranolol does not stimulate muscarinic receptors.

Why is "Reduced clearance of catecholamines" not the answer?

Propranolol does not meaningfully slow the clearance of catecholamines.

Why is "Increased renin release by the drug" not the answer?

Beta blockade reduces renin release, so this would lower rather than raise pressure.

What concept does this question test?

It tests Autonomic nervous system: pheochromocytoma and beta-blockade in Pharmacology. Blocking beta receptors first leaves alpha effects unopposed and the pressure rises. Alpha blockade with phenoxybenzamine is started before any beta-blocker.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Autonomic nervous system: pheochromocytoma and beta-blockade?

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.