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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 in dependence?

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.

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Pharmacodynamics: partial… MCQ (B7-PHARM5-5)

Q: What is the answer to this Pharmacology question?

The best answer is C, A high-affinity partial agonist displaces the full agonist from mu receptors and gives less receptor activation. Buprenorphine binds mu receptors with very high affinity but low intrinsic activity.

Q: What concept does this question test?

It tests Pharmacodynamics: partial agonist in dependence in Pharmacology. In a patient with receptors occupied by a full agonist, it displaces methadone and the net receptor activation falls, which precipitates withdrawal. The same property makes it a ceiling-limited analgesic with a lower risk of respiratory depression.

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Pharmacology · Pharmacodynamics: partial agonist in dependence

Sample item

A man stable on methadone maintenance is given sublingual buprenorphine for a pain complaint and within an hour develops sweating, yawning, abdominal cramps and mydriasis. What is the mechanism?

ABuprenorphine induces CYP3A4 and rapidly lowers methadone concentrationBBuprenorphine acts as an inverse agonist and shuts down basal mu receptor signallingCA high-affinity partial agonist displaces the full agonist from mu receptors and gives less receptor activationDBuprenorphine is a kappa agonist that reverses mu-mediated effects

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

The answer and the reasoning

C. A high-affinity partial agonist displaces the full agonist from mu receptors and gives less receptor activation

Buprenorphine binds mu receptors with very high affinity but low intrinsic activity. In a patient with receptors occupied by a full agonist, it displaces methadone and the net receptor activation falls, which precipitates withdrawal. The same property makes it a ceiling-limited analgesic with a lower risk of respiratory depression.

Option by option

A. Buprenorphine induces CYP3A4 and rapidly lowers methadone concentration
Enzyme induction would take days and is not the mechanism of this rapid event.
B. Buprenorphine acts as an inverse agonist and shuts down basal mu receptor signalling
Buprenorphine is a partial agonist, not an inverse agonist, at the mu receptor.
C. A high-affinity partial agonist displaces the full agonist from mu receptors and gives less receptor activation (correct)
Correct. Displacement of a full agonist by a partial agonist lowers net efficacy and produces withdrawal.
D. Buprenorphine is a kappa agonist that reverses mu-mediated effects
Its kappa activity is antagonistic and does not account for this onset of withdrawal.

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.

Pharmacodynamics: partial agonist in dependence: practice question

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The answer and the reasoning

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