Pharmacology: ephedrine tachyphylaxis: practice question

A Anaesthesia 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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Anaesthesia · Pharmacology: ephedrine tachyphylaxis

Sample item

Repeated doses of ephedrine produce progressively less pressor response. What explains this tachyphylaxis?

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

The answer and the reasoning

A. Depletion of noradrenaline stores because of its indirect action

Ephedrine acts partly directly on adrenergic receptors and partly indirectly by releasing noradrenaline from nerve terminals. With repeated dosing the stores are depleted, so the response declines. Direct-acting agents such as phenylephrine do not show this effect.

Option by option

  • A. Depletion of noradrenaline stores because of its indirect action (correct)

    Correct. Indirect release depletes noradrenaline stores.

  • B. Rapid renal clearance of ephedrine

    Clearance does not explain the falling response to repeated doses.

  • C. Upregulation of alpha-1 receptors

    Receptor upregulation would increase and not reduce the response.

  • D. Development of antibodies to ephedrine

    Antibody formation is not the mechanism.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is A, Depletion of noradrenaline stores because of its indirect action. Ephedrine acts partly directly on adrenergic receptors and partly indirectly by releasing noradrenaline from nerve terminals.

Why is "Rapid renal clearance of ephedrine" not the answer?

Clearance does not explain the falling response to repeated doses.

Why is "Upregulation of alpha-1 receptors" not the answer?

Receptor upregulation would increase and not reduce the response.

Why is "Development of antibodies to ephedrine" not the answer?

Antibody formation is not the mechanism.

What concept does this question test?

It tests Pharmacology: ephedrine tachyphylaxis in Anaesthesia. With repeated dosing the stores are depleted, so the response declines. Direct-acting agents such as phenylephrine do not show this effect.

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 Pharmacology: ephedrine tachyphylaxis?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia 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.