Psychopharmacology: dopamine receptor occupancy: 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: dopamine receptor occupancy

Sample item

Imaging studies relate antipsychotic response and side effects to D2 receptor occupancy. Which statement is correct?

AParkinsonism appears only below 40 percent occupancyBResponse needs more than 90 percent occupancy to be seenCResponse is seen at about 65 to 80 percent occupancy and parkinsonism rises above about 80 percentDResponse and parkinsonism both begin only at 100 percent occupancy

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

The answer and the reasoning

C. Response is seen at about 65 to 80 percent occupancy and parkinsonism rises above about 80 percent

PET studies show a therapeutic window of roughly 65 to 80 percent striatal D2 occupancy. Above about 80 percent the risk of extrapyramidal symptoms and prolactin elevation rises sharply. This is why doses higher than needed add side effects without more benefit.

Option by option

A. Parkinsonism appears only below 40 percent occupancy
Parkinsonism rises with higher, not lower, occupancy.
B. Response needs more than 90 percent occupancy to be seen
Occupancy above 90 percent is not required and would cause marked side effects.
C. Response is seen at about 65 to 80 percent occupancy and parkinsonism rises above about 80 percent (correct)
Correct. This is the therapeutic window described in occupancy studies.
D. Response and parkinsonism both begin only at 100 percent occupancy
Occupancy of 100 percent is not needed for response and would be intolerable.

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.

Questions about this Psychiatry question

What is the answer to this Psychiatry question?

The best answer is C, Response is seen at about 65 to 80 percent occupancy and parkinsonism rises above about 80 percent. PET studies show a therapeutic window of roughly 65 to 80 percent striatal D2 occupancy.

Why is "Parkinsonism appears only below 40 percent occupancy" not the answer?

Parkinsonism rises with higher, not lower, occupancy.

Why is "Response needs more than 90 percent occupancy to be seen" not the answer?

Occupancy above 90 percent is not required and would cause marked side effects.

Why is "Response and parkinsonism both begin only at 100 percent occupancy" not the answer?

Occupancy of 100 percent is not needed for response and would be intolerable.

What concept does this question test?

It tests Psychopharmacology: dopamine receptor occupancy in Psychiatry. Above about 80 percent the risk of extrapyramidal symptoms and prolactin elevation rises sharply. This is why doses higher than needed add side effects without more benefit.

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: dopamine receptor occupancy?

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.