General pharmacology: enzyme inducer interaction: 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 · General pharmacology: enzyme inducer interaction

Sample item

A renal transplant recipient stable on cyclosporine starts a herbal preparation of St John's wort for low mood, and graft rejection follows. What explains this?

AInhibition of CYP3A4 raising cyclosporine levelsBEnhanced renal excretion by urinary acidificationCInduction of CYP3A4 lowering cyclosporine levelsDDisplacement of cyclosporine from plasma proteins

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

The answer and the reasoning

C. Induction of CYP3A4 lowering cyclosporine levels

St John's wort induces CYP3A4 and P-glycoprotein, which lowers blood levels of cyclosporine, tacrolimus and other substrates. Subtherapeutic immunosuppression can lead to rejection.

Option by option

A. Inhibition of CYP3A4 raising cyclosporine levels
Inhibition would raise levels and cause toxicity rather than rejection.
B. Enhanced renal excretion by urinary acidification
St John's wort does not acidify urine; the interaction is enzymatic.
C. Induction of CYP3A4 lowering cyclosporine levels (correct)
Correct. Enzyme induction reduces the immunosuppressant concentration.
D. Displacement of cyclosporine from plasma proteins
Protein-binding displacement is not the mechanism of this interaction.

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 C, Induction of CYP3A4 lowering cyclosporine levels. St John's wort induces CYP3A4 and P-glycoprotein, which lowers blood levels of cyclosporine, tacrolimus and other substrates.

Why is "Inhibition of CYP3A4 raising cyclosporine levels" not the answer?

Inhibition would raise levels and cause toxicity rather than rejection.

Why is "Enhanced renal excretion by urinary acidification" not the answer?

St John's wort does not acidify urine; the interaction is enzymatic.

Why is "Displacement of cyclosporine from plasma proteins" not the answer?

Protein-binding displacement is not the mechanism of this interaction.

What concept does this question test?

It tests General pharmacology: enzyme inducer interaction in Pharmacology. Subtherapeutic immunosuppression can lead to rejection.

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 General pharmacology: enzyme inducer interaction?

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.