GI drugs: domperidone: practice question

A Pharmacology 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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Pharmacology · GI drugs: domperidone

Sample item

A patient on domperidone for gastroparesis is also given clarithromycin. What is the main risk?

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

The answer and the reasoning

A. QT prolongation and torsades because of CYP3A4 inhibition raising domperidone levels

Domperidone is a peripheral D2 blocker that does not cross the blood-brain barrier well, so extrapyramidal effects are uncommon, but it prolongs the QT interval. CYP3A4 inhibitors such as clarithromycin and ketoconazole raise its levels and increase arrhythmia risk.

Option by option

  • A. QT prolongation and torsades because of CYP3A4 inhibition raising domperidone levels (correct)

    Correct. Added QT prolongation and raised drug levels increase torsades risk.

  • B. Serotonin syndrome

    Serotonin syndrome is not expected with this pair.

  • C. Extrapyramidal rigidity from central D2 blockade

    Extrapyramidal effects are minimal because of poor CNS entry.

  • D. Respiratory depression

    Respiratory depression is not a feature.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is A, QT prolongation and torsades because of CYP3A4 inhibition raising domperidone levels. Domperidone is a peripheral D2 blocker that does not cross the blood-brain barrier well, so extrapyramidal effects are uncommon, but it prolongs the QT interval.

Why is "Serotonin syndrome" not the answer?

Serotonin syndrome is not expected with this pair.

Why is "Extrapyramidal rigidity from central D2 blockade" not the answer?

Extrapyramidal effects are minimal because of poor CNS entry.

Why is "Respiratory depression" not the answer?

Respiratory depression is not a feature.

What concept does this question test?

It tests GI drugs: domperidone in Pharmacology. CYP3A4 inhibitors such as clarithromycin and ketoconazole raise its levels and increase arrhythmia risk.

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 GI drugs: domperidone?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.