Toxicology: ethylene glycol: 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: ethylene glycol

Sample item

A man with ethylene glycol poisoning is unable to get fomepizole at a remote hospital, and ethanol infusion is considered. What is the rationale?

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

The answer and the reasoning

C. Ethanol is the preferred substrate for alcohol dehydrogenase and competitively blocks formation of toxic metabolites

Alcohol dehydrogenase has a much higher affinity for ethanol than for ethylene glycol or methanol. Ethanol thus occupies the enzyme and delays formation of glycolic and oxalic acids, allowing unchanged parent compound to be excreted or dialysed. Fomepizole is preferred as it is a more predictable inhibitor, with fewer sedative effects and no need for level monitoring.

Option by option

  • A. Ethanol increases renal excretion of ethylene glycol

    Ethanol does not change renal handling of ethylene glycol.

  • B. Ethanol induces conjugation of ethylene glycol

    Ethanol does not accelerate conjugation of ethylene glycol.

  • C. Ethanol is the preferred substrate for alcohol dehydrogenase and competitively blocks formation of toxic metabolites (correct)

    Competition for alcohol dehydrogenase limits generation of toxic acids.

  • D. Ethanol chelates oxalate in the blood

    Ethanol is not a chelator of oxalate.

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 C, Ethanol is the preferred substrate for alcohol dehydrogenase and competitively blocks formation of toxic metabolites. Alcohol dehydrogenase has a much higher affinity for ethanol than for ethylene glycol or methanol.

Why is "Ethanol increases renal excretion of ethylene glycol" not the answer?

Ethanol does not change renal handling of ethylene glycol.

Why is "Ethanol induces conjugation of ethylene glycol" not the answer?

Ethanol does not accelerate conjugation of ethylene glycol.

Why is "Ethanol chelates oxalate in the blood" not the answer?

Ethanol is not a chelator of oxalate.

What concept does this question test?

It tests Toxicology: ethylene glycol in Pharmacology. Ethanol thus occupies the enzyme and delays formation of glycolic and oxalic acids, allowing unchanged parent compound to be excreted or dialysed. Fomepizole is preferred as it is a more predictable inhibitor, with fewer sedative effects and no need for level monitoring.

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: ethylene glycol?

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.