Anticancer drugs: methotrexate rescue: 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 · Anticancer drugs: methotrexate rescue

Sample item

After high-dose methotrexate chemotherapy, leucovorin is administered. What is its purpose?

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

The answer and the reasoning

B. To rescue normal cells by bypassing dihydrofolate reductase blockade

Leucovorin (folinic acid) is a reduced folate that can be used without dihydrofolate reductase, limiting toxicity to normal tissues after high-dose methotrexate. Urine is alkalinised, not acidified, to aid methotrexate elimination.

Option by option

  • A. To acidify urine and trap methotrexate

    Alkalinisation reduces renal precipitation of methotrexate.

  • B. To rescue normal cells by bypassing dihydrofolate reductase blockade (correct)

    Correct. It replenishes reduced folate downstream of DHFR.

  • C. To inhibit xanthine oxidase

    Allopurinol and febuxostat inhibit xanthine oxidase.

  • D. To enhance methotrexate binding to DNA

    Leucovorin reduces toxicity; it does not enhance cytotoxic binding.

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 B, To rescue normal cells by bypassing dihydrofolate reductase blockade. Leucovorin (folinic acid) is a reduced folate that can be used without dihydrofolate reductase, limiting toxicity to normal tissues after high-dose methotrexate.

Why is "To acidify urine and trap methotrexate" not the answer?

Alkalinisation reduces renal precipitation of methotrexate.

Why is "To inhibit xanthine oxidase" not the answer?

Allopurinol and febuxostat inhibit xanthine oxidase.

Why is "To enhance methotrexate binding to DNA" not the answer?

Leucovorin reduces toxicity; it does not enhance cytotoxic binding.

What concept does this question test?

It tests Anticancer drugs: methotrexate rescue in Pharmacology. Urine is alkalinised, not acidified, to aid methotrexate elimination.

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 Anticancer drugs: methotrexate rescue?

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.