Adrenergic drugs: isoprenaline: 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 · Adrenergic drugs: isoprenaline

Sample item

A healthy volunteer receives an intravenous infusion of isoprenaline in a pharmacology experiment. Which combination of cardiovascular effects is expected?

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

The answer and the reasoning

D. Tachycardia with a fall in diastolic and mean arterial pressure

Isoprenaline is a non-selective beta agonist with almost no alpha action. Beta1 stimulation raises heart rate and contractility, while beta2 stimulation dilates skeletal muscle arterioles and lowers peripheral resistance, so diastolic and mean pressures fall. Reflex vagal slowing does not occur because mean pressure falls.

Option by option

  • A. Bradycardia with a rise in diastolic and mean arterial pressure

    A rise in pressure with reflex bradycardia is the pattern of noradrenaline, which has strong alpha1 action.

  • B. Tachycardia with a rise in diastolic and mean arterial pressure

    Isoprenaline has almost no alpha1 action, so there is no vasoconstriction to raise diastolic pressure; beta2 vasodilatation lowers it.

  • C. Bradycardia with a fall in diastolic and mean arterial pressure

    Bradycardia would require a pressor rise with reflex vagal action, which does not occur when mean pressure falls.

  • D. Tachycardia with a fall in diastolic and mean arterial pressure (correct)

    Correct. Beta1 stimulation speeds the heart while beta2 vasodilatation lowers diastolic and mean pressure.

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, Tachycardia with a fall in diastolic and mean arterial pressure. Isoprenaline is a non-selective beta agonist with almost no alpha action.

Why is "Bradycardia with a rise in diastolic and mean arterial pressure" not the answer?

A rise in pressure with reflex bradycardia is the pattern of noradrenaline, which has strong alpha1 action.

Why is "Tachycardia with a rise in diastolic and mean arterial pressure" not the answer?

Isoprenaline has almost no alpha1 action, so there is no vasoconstriction to raise diastolic pressure; beta2 vasodilatation lowers it.

Why is "Bradycardia with a fall in diastolic and mean arterial pressure" not the answer?

Bradycardia would require a pressor rise with reflex vagal action, which does not occur when mean pressure falls.

What concept does this question test?

It tests Adrenergic drugs: isoprenaline in Pharmacology. Beta1 stimulation raises heart rate and contractility, while beta2 stimulation dilates skeletal muscle arterioles and lowers peripheral resistance, so diastolic and mean pressures fall. Reflex vagal slowing does not occur because mean pressure falls.

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 Adrenergic drugs: isoprenaline?

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.