Antifungals: flucytosine: 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 · Antifungals: flucytosine

Sample item

Flucytosine is combined with amphotericin B for cryptococcal meningitis. Which statement about it is correct?

AIt is used alone as it has no resistanceBIt inhibits ergosterol synthesisCIt is converted to 5-fluorouracil in fungal cells and can cause bone marrow suppressionDIt is converted to 5-FU by human enzymes only

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

The answer and the reasoning

C. It is converted to 5-fluorouracil in fungal cells and can cause bone marrow suppression

Fungal cytosine deaminase converts flucytosine into 5-fluorouracil, which inhibits DNA and RNA synthesis, with human cells lacking much of this enzyme. Marrow suppression and hepatotoxicity occur, and resistance develops rapidly, so it is given in combination.

Option by option

A. It is used alone as it has no resistance
Resistance emerges quickly with monotherapy.
B. It inhibits ergosterol synthesis
Ergosterol synthesis inhibition is the azole mechanism.
C. It is converted to 5-fluorouracil in fungal cells and can cause bone marrow suppression (correct)
Correct. Conversion to 5-FU occurs in fungal cells, and marrow suppression is a risk.
D. It is converted to 5-FU by human enzymes only
Fungal, not human, enzymes convert it.

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, It is converted to 5-fluorouracil in fungal cells and can cause bone marrow suppression. Fungal cytosine deaminase converts flucytosine into 5-fluorouracil, which inhibits DNA and RNA synthesis, with human cells lacking much of this enzyme.

Why is "It is used alone as it has no resistance" not the answer?

Resistance emerges quickly with monotherapy.

Why is "It inhibits ergosterol synthesis" not the answer?

Ergosterol synthesis inhibition is the azole mechanism.

Why is "It is converted to 5-FU by human enzymes only" not the answer?

Fungal, not human, enzymes convert it.

What concept does this question test?

It tests Antifungals: flucytosine in Pharmacology. Marrow suppression and hepatotoxicity occur, and resistance develops rapidly, so it is given in combination.

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 Antifungals: flucytosine?

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.