Substance use: naloxone duration of action: practice question

A Psychiatry 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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Psychiatry · Substance use: naloxone duration of action

Sample item

A man with heroin overdose recovers fully after intravenous naloxone and refuses admission. Ninety minutes later he is found drowsy with a respiratory rate of 6 per minute. What is the most likely explanation?

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

The answer and the reasoning

C. Naloxone acts for a shorter time than the opioid

Naloxone is a competitive opioid antagonist with a short duration of action of roughly 30 to 90 minutes, shorter than many opioids such as methadone. Once it wears off, opioid effects can return (renarcotisation), so patients need observation and repeated or infused doses.

Option by option

  • A. Naloxone acts only on delta receptors

    Naloxone antagonises mu, delta and kappa receptors, with the greatest affinity for mu.

  • B. Naloxone is itself a respiratory depressant when metabolised

    Naloxone has no intrinsic respiratory depressant action.

  • C. Naloxone acts for a shorter time than the opioid (correct)

    Correct. Short-acting antagonist, longer-acting opioid, so toxicity returns.

  • D. Tolerance to naloxone developed

    Tolerance to an antagonist does not develop within an hour and does not explain recurrence.

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 Psychiatry question

What is the answer to this Psychiatry question?

The best answer is C, Naloxone acts for a shorter time than the opioid. Naloxone is a competitive opioid antagonist with a short duration of action of roughly 30 to 90 minutes, shorter than many opioids such as methadone.

Why is "Naloxone acts only on delta receptors" not the answer?

Naloxone antagonises mu, delta and kappa receptors, with the greatest affinity for mu.

Why is "Naloxone is itself a respiratory depressant when metabolised" not the answer?

Naloxone has no intrinsic respiratory depressant action.

Why is "Tolerance to naloxone developed" not the answer?

Tolerance to an antagonist does not develop within an hour and does not explain recurrence.

What concept does this question test?

It tests Substance use: naloxone duration of action in Psychiatry. Once it wears off, opioid effects can return (renarcotisation), so patients need observation and repeated or infused doses.

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 Substance use: naloxone duration of action?

Learn each diagnosis by its core features and its first-line treatment. Then use the flashcards and the other Psychiatry 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.