Toxicology: long-acting anticoagulant rodenticide: 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 · Toxicology: long-acting anticoagulant rodenticide

Sample item

A 20-year-old woman who ingested a brodifacoum-based rat poison presents on day 3 with epistaxis, an INR of 8 and a prolonged prothrombin time. Intravenous vitamin K1 corrects the INR within hours. Why must vitamin K be continued for weeks to months in this poisoning?

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

The answer and the reasoning

D. The lipophilic superwarfarin has a very long half-life and persists in the liver

Brodifacoum and related superwarfarins are highly lipophilic, bind strongly to hepatic vitamin K epoxide reductase and have half-lives of weeks. Their effect outlasts a single vitamin K dose, so repeated dosing is needed, often for weeks to months, with regular INR monitoring. Conventional warfarin overdose needs only a short course.

Option by option

  • A. Vitamin K is cleared within minutes and needs constant replacement in any poisoning

    Vitamin K has a short duration, but this is also true for warfarin, and does not explain the difference.

  • B. Superwarfarins irreversibly destroy clotting factors

    Superwarfarins inhibit factor synthesis rather than destroying existing factors.

  • C. Vitamin K is hepatotoxic and must be given in low daily doses

    Vitamin K is not hepatotoxic at these doses, and under-dosing would leave the patient at risk.

  • D. The lipophilic superwarfarin has a very long half-life and persists in the liver (correct)

    Prolonged hepatic retention of the superwarfarin keeps the inhibition active for weeks.

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, The lipophilic superwarfarin has a very long half-life and persists in the liver. Brodifacoum and related superwarfarins are highly lipophilic, bind strongly to hepatic vitamin K epoxide reductase and have half-lives of weeks.

Why is "Vitamin K is cleared within minutes and needs constant replacement in…" not the answer?

Vitamin K has a short duration, but this is also true for warfarin, and does not explain the difference.

Why is "Superwarfarins irreversibly destroy clotting factors" not the answer?

Superwarfarins inhibit factor synthesis rather than destroying existing factors.

Why is "Vitamin K is hepatotoxic and must be given in low daily doses" not the answer?

Vitamin K is not hepatotoxic at these doses, and under-dosing would leave the patient at risk.

What concept does this question test?

It tests Toxicology: long-acting anticoagulant rodenticide in Pharmacology. Their effect outlasts a single vitamin K dose, so repeated dosing is needed, often for weeks to months, with regular INR monitoring. Conventional warfarin overdose needs only a short course.

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 Toxicology: long-acting anticoagulant rodenticide?

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.