Psychopharmacology: CYP2D6 poor metabolisers: 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 · Psychopharmacology: CYP2D6 poor metabolisers

Sample item

A patient who is a CYP2D6 poor metaboliser develops marked sedation and QT prolongation on a standard dose of nortriptyline. The best explanation is

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

The answer and the reasoning

C. Reduced metabolism raising plasma levels of the drug

CYP2D6 metabolises many antidepressants and antipsychotics, including tricyclics, paroxetine, fluoxetine, risperidone and haloperidol. Poor metabolisers accumulate the drug, so dose reduction or monitoring is needed. Ultra-rapid metabolisers may fail to respond.

Option by option

  • A. Increased conversion to an inactive metabolite

    Poor metabolisers produce less, not more, metabolite.

  • B. Reduced absorption

    Absorption is not the issue.

  • C. Reduced metabolism raising plasma levels of the drug (correct)

    Correct. Reduced metabolism raises drug levels and toxicity.

  • D. Excess renal clearance

    Clearance falls rather than rises.

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, Reduced metabolism raising plasma levels of the drug. CYP2D6 metabolises many antidepressants and antipsychotics, including tricyclics, paroxetine, fluoxetine, risperidone and haloperidol.

Why is "Increased conversion to an inactive metabolite" not the answer?

Poor metabolisers produce less, not more, metabolite.

Why is "Reduced absorption" not the answer?

Absorption is not the issue.

Why is "Excess renal clearance" not the answer?

Clearance falls rather than rises.

What concept does this question test?

It tests Psychopharmacology: CYP2D6 poor metabolisers in Psychiatry. Poor metabolisers accumulate the drug, so dose reduction or monitoring is needed. Ultra-rapid metabolisers may fail to respond.

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 Psychopharmacology: CYP2D6 poor metabolisers?

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.