Psychopharmacology: CYP interactions: 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: CYP interactions

Sample item

Fluoxetine and paroxetine can raise plasma levels of many tricyclics and impair activation of prodrugs such as codeine and tamoxifen, by inhibiting which enzyme?

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

The answer and the reasoning

C. CYP2D6

Fluoxetine and paroxetine are strong CYP2D6 inhibitors, which raises levels of TCAs, antipsychotics and some beta blockers, and reduces activation of prodrugs like codeine and tamoxifen. Fluoxetine's long half-life prolongs the effect.

Option by option

  • A. CYP1A2

    CYP1A2 inhibition is characteristic of fluvoxamine.

  • B. CYP2E1

    CYP2E1 is mainly relevant to alcohol and paracetamol.

  • C. CYP2D6 (correct)

    Correct. CYP2D6 inhibition underlies the interaction.

  • D. CYP3A4 induction

    Induction of CYP3A4 is typical of carbamazepine, not these SSRIs.

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, CYP2D6. Fluoxetine and paroxetine are strong CYP2D6 inhibitors, which raises levels of TCAs, antipsychotics and some beta blockers, and reduces activation of prodrugs like codeine and tamoxifen.

Why is "CYP1A2" not the answer?

CYP1A2 inhibition is characteristic of fluvoxamine.

Why is "CYP2E1" not the answer?

CYP2E1 is mainly relevant to alcohol and paracetamol.

Why is "CYP3A4 induction" not the answer?

Induction of CYP3A4 is typical of carbamazepine, not these SSRIs.

What concept does this question test?

It tests Psychopharmacology: CYP interactions in Psychiatry. Fluoxetine's long half-life prolongs the 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 Psychopharmacology: CYP interactions?

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.