Chemotherapy: etoposide mechanism: 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 · Chemotherapy: etoposide mechanism

Sample item

A man with small cell lung cancer is treated with cisplatin and etoposide. What is the mechanism of etoposide?

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

The answer and the reasoning

D. Topoisomerase II inhibition causing double-strand DNA breaks

Etoposide stabilises the topoisomerase II-DNA cleavable complex, leaving double-strand breaks in the S and G2 phases. Irinotecan and topotecan inhibit topoisomerase I, taxanes stabilise microtubules, and fluorouracil inhibits thymidylate synthase. Secondary leukaemia is a late complication.

Option by option

  • A. Microtubule stabilisation causing mitotic arrest

    Microtubule stabilisation is the action of the taxanes.

  • B. Thymidylate synthase inhibition causing thymine depletion

    Thymidylate synthase inhibition is the action of fluorouracil.

  • C. Topoisomerase I inhibition causing single-strand DNA breaks

    Topoisomerase I inhibition is the action of irinotecan and topotecan.

  • D. Topoisomerase II inhibition causing double-strand DNA breaks (correct)

    Correct. It traps topoisomerase II on DNA and produces double-strand breaks.

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 D, Topoisomerase II inhibition causing double-strand DNA breaks. Etoposide stabilises the topoisomerase II-DNA cleavable complex, leaving double-strand breaks in the S and G2 phases.

Why is "Microtubule stabilisation causing mitotic arrest" not the answer?

Microtubule stabilisation is the action of the taxanes.

Why is "Thymidylate synthase inhibition causing thymine depletion" not the answer?

Thymidylate synthase inhibition is the action of fluorouracil.

Why is "Topoisomerase I inhibition causing single-strand DNA breaks" not the answer?

Topoisomerase I inhibition is the action of irinotecan and topotecan.

What concept does this question test?

It tests Chemotherapy: etoposide mechanism in Pharmacology. Irinotecan and topotecan inhibit topoisomerase I, taxanes stabilise microtubules, and fluorouracil inhibits thymidylate synthase. Secondary leukaemia is a late complication.

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 Chemotherapy: etoposide mechanism?

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.