Toxicology and antidotes: lead encephalopathy chelation: 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: lead encephalopathy chelation

Sample item

A 3-year-old child with pica has a blood lead level of 110 micrograms/dL, persistent vomiting, ataxia and a generalised seizure. Which chelation regimen is appropriate?

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

The answer and the reasoning

D. Dimercaprol followed by calcium disodium edetate

Lead encephalopathy is a medical emergency. Dimercaprol is given first, followed by calcium disodium EDTA, because EDTA alone can mobilise lead into the brain. Succimer alone is for lead levels without encephalopathy. Calcium disodium EDTA must be used, as disodium EDTA causes hypocalcaemia.

Option by option

  • A. Intravenous deferoxamine

    Deferoxamine chelates iron and aluminium and is not used for lead.

  • B. Oral penicillamine alone

    Oral penicillamine alone is a weaker alternative and is not adequate for encephalopathy.

  • C. Oral succimer alone

    Oral succimer alone is suitable for symptomless children with moderately raised levels, not for encephalopathy.

  • D. Dimercaprol followed by calcium disodium edetate (correct)

    Correct. Combined dimercaprol and calcium disodium edetate is used for lead encephalopathy.

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, Dimercaprol followed by calcium disodium edetate. Lead encephalopathy is a medical emergency.

Why is "Intravenous deferoxamine" not the answer?

Deferoxamine chelates iron and aluminium and is not used for lead.

Why is "Oral penicillamine alone" not the answer?

Oral penicillamine alone is a weaker alternative and is not adequate for encephalopathy.

Why is "Oral succimer alone" not the answer?

Oral succimer alone is suitable for symptomless children with moderately raised levels, not for encephalopathy.

What concept does this question test?

It tests Toxicology and antidotes: lead encephalopathy chelation in Pharmacology. Dimercaprol is given first, followed by calcium disodium EDTA, because EDTA alone can mobilise lead into the brain. Succimer alone is for lead levels without encephalopathy. Calcium disodium EDTA must be used, as disodium EDTA causes hypocalcaemia.

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 and antidotes: lead encephalopathy chelation?

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.