Pharmacodynamics: partial agonist: 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.

Try it

Pharmacology · Pharmacodynamics: partial agonist

Sample item

A man maintained on methadone for opioid dependence is given sublingual buprenorphine by mistake. Within an hour he has sweating, yawning, abdominal cramps and dilated pupils. What explains this?

ABuprenorphine is a full agonist producing overdose-related excitationBA high-affinity partial agonist that displaces methadone from mu receptorsCBuprenorphine is a pure antagonist at mu receptorsDBuprenorphine induces CYP3A4 and rapidly eliminates methadone

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

The answer and the reasoning

B. A high-affinity partial agonist that displaces methadone from mu receptors

Buprenorphine binds mu receptors with high affinity but has low intrinsic activity. It displaces a full agonist such as methadone and replaces it with weaker stimulation, precipitating withdrawal in a physically dependent patient. Pure antagonists such as naloxone precipitate withdrawal through a different mechanism.

Option by option

A. Buprenorphine is a full agonist producing overdose-related excitation
It is not a full agonist, and overdose would cause sedation and miosis rather than withdrawal.
B. A high-affinity partial agonist that displaces methadone from mu receptors (correct)
Correct. High affinity with low efficacy displaces the full agonist and reduces total opioid effect.
C. Buprenorphine is a pure antagonist at mu receptors
It is a partial agonist and not a pure antagonist; naloxone is the pure antagonist.
D. Buprenorphine induces CYP3A4 and rapidly eliminates methadone
Induction would take days, not an hour, and buprenorphine is not a significant inducer.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, A high-affinity partial agonist that displaces methadone from mu receptors. Buprenorphine binds mu receptors with high affinity but has low intrinsic activity.

Why is "Buprenorphine is a full agonist producing overdose-related excitation" not the answer?

It is not a full agonist, and overdose would cause sedation and miosis rather than withdrawal.

Why is "Buprenorphine is a pure antagonist at mu receptors" not the answer?

It is a partial agonist and not a pure antagonist; naloxone is the pure antagonist.

Why is "Buprenorphine induces CYP3A4 and rapidly eliminates methadone" not the answer?

Induction would take days, not an hour, and buprenorphine is not a significant inducer.

What concept does this question test?

It tests Pharmacodynamics: partial agonist in Pharmacology. It displaces a full agonist such as methadone and replaces it with weaker stimulation, precipitating withdrawal in a physically dependent patient. Pure antagonists such as naloxone precipitate withdrawal through a different mechanism.

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 Pharmacodynamics: partial agonist?

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.