Pain: codeine and CYP2D6: 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.

Try it

Anaesthesia · Pain: codeine and CYP2D6

Sample item

Why is codeine contraindicated in children after tonsillectomy?

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

The answer and the reasoning

D. Ultrarapid CYP2D6 metabolisers convert it to excess morphine, causing respiratory depression

Codeine is a prodrug that is converted to morphine by CYP2D6. In ultrarapid metabolisers, particularly children with obstructive sleep-disordered breathing, this produces dangerous morphine levels and fatal respiratory depression. Regulatory agencies advise against its use after tonsillectomy in children.

Option by option

  • A. It is an ester that causes allergy

    Codeine is a phenanthrene opioid and not an ester.

  • B. It causes malignant hyperthermia

    Codeine is not a trigger of malignant hyperthermia.

  • C. It is metabolised to inactive compounds that accumulate

    The concern is excess active metabolite and not inactive accumulation.

  • D. Ultrarapid CYP2D6 metabolisers convert it to excess morphine, causing respiratory depression (correct)

    Correct. Ultrarapid conversion to morphine leads to toxicity.

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.

More Anaesthesia questions

Questions about this Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is D, Ultrarapid CYP2D6 metabolisers convert it to excess morphine, causing respiratory depression. Codeine is a prodrug that is converted to morphine by CYP2D6.

Why is "It is an ester that causes allergy" not the answer?

Codeine is a phenanthrene opioid and not an ester.

Why is "It causes malignant hyperthermia" not the answer?

Codeine is not a trigger of malignant hyperthermia.

Why is "It is metabolised to inactive compounds that accumulate" not the answer?

The concern is excess active metabolite and not inactive accumulation.

What concept does this question test?

It tests Pain: codeine and CYP2D6 in Anaesthesia. In ultrarapid metabolisers, particularly children with obstructive sleep-disordered breathing, this produces dangerous morphine levels and fatal respiratory depression. Regulatory agencies advise against its use after tonsillectomy in children.

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 Pain: codeine and CYP2D6?

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.