Toxicology and antidotes: dialysis and tricyclic overdose: 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 and antidotes: dialysis and tricyclic overdose

Sample item

Which overdosed drug is least likely to be removed by haemodialysis because of its large volume of distribution and high protein binding?

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

The answer and the reasoning

A. Amitriptyline

Haemodialysis removes small, water-soluble, poorly protein-bound drugs with a small volume of distribution, such as lithium, methanol, ethylene glycol and salicylate. Tricyclic antidepressants are highly lipophilic and protein bound, with a very large volume of distribution, so dialysis is ineffective.

Option by option

  • A. Amitriptyline (correct)

    Correct. Amitriptyline is lipophilic, highly protein bound and widely distributed in tissues.

  • B. Lithium

    Lithium is small, water-soluble and not protein bound, so dialysis removes it well.

  • C. Salicylate

    Salicylate is dialysable and dialysis is used in severe poisoning.

  • D. Methanol

    Methanol is a small molecule that is readily dialysed, together with its toxic metabolite.

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 A, Amitriptyline. Haemodialysis removes small, water-soluble, poorly protein-bound drugs with a small volume of distribution, such as lithium, methanol, ethylene glycol and salicylate.

Why is "Lithium" not the answer?

Lithium is small, water-soluble and not protein bound, so dialysis removes it well.

Why is "Salicylate" not the answer?

Salicylate is dialysable and dialysis is used in severe poisoning.

Why is "Methanol" not the answer?

Methanol is a small molecule that is readily dialysed, together with its toxic metabolite.

What concept does this question test?

It tests Toxicology and antidotes: dialysis and tricyclic overdose in Pharmacology. Tricyclic antidepressants are highly lipophilic and protein bound, with a very large volume of distribution, so dialysis is ineffective.

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 Toxicology and antidotes: dialysis and tricyclic overdose?

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.