Antifungals: terbinafine: 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.

Try it

Pharmacology · Antifungals: terbinafine

Sample item

A 40-year-old man has distal subungual onychomycosis due to a dermatophyte and is started on terbinafine. What is its mechanism of action?

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

The answer and the reasoning

A. Inhibition of squalene epoxidase, blocking ergosterol synthesis

Terbinafine, an allylamine, inhibits squalene epoxidase. Ergosterol is depleted and squalene accumulates to toxic levels, giving fungicidal activity against dermatophytes. Hepatotoxicity and taste disturbance are the main adverse effects.

Option by option

  • A. Inhibition of squalene epoxidase, blocking ergosterol synthesis (correct)

    Correct. Squalene epoxidase blockade causes ergosterol deficiency and squalene accumulation.

  • B. Inhibition of lanosterol 14-alpha-demethylase

    14-alpha-demethylase inhibition is the action of azoles such as fluconazole.

  • C. Inhibition of beta-1,3-glucan synthase

    Glucan synthase inhibition is the action of echinocandins such as caspofungin.

  • D. Binding to ergosterol to form membrane pores

    Pore formation by binding ergosterol is the action of amphotericin B and nystatin.

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.

More Pharmacology questions

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is A, Inhibition of squalene epoxidase, blocking ergosterol synthesis. Terbinafine, an allylamine, inhibits squalene epoxidase.

Why is "Inhibition of lanosterol 14-alpha-demethylase" not the answer?

14-alpha-demethylase inhibition is the action of azoles such as fluconazole.

Why is "Inhibition of beta-1,3-glucan synthase" not the answer?

Glucan synthase inhibition is the action of echinocandins such as caspofungin.

Why is "Binding to ergosterol to form membrane pores" not the answer?

Pore formation by binding ergosterol is the action of amphotericin B and nystatin.

What concept does this question test?

It tests Antifungals: terbinafine in Pharmacology. Ergosterol is depleted and squalene accumulates to toxic levels, giving fungicidal activity against dermatophytes. Hepatotoxicity and taste disturbance are the main adverse effects.

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: terbinafine?

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.