Toxicology: neostigmine in neurotoxic snakebite: practice question

A Forensic Medicine 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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Forensic Medicine · Toxicology: neostigmine in neurotoxic snakebite

Sample item

A patient bitten by a cobra has ptosis and limb weakness that persist after adequate antisnake venom. Which drug combination may improve neuromuscular transmission?

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

The answer and the reasoning

D. Neostigmine with atropine

Cobra neurotoxin acts at the postsynaptic acetylcholine receptors, in a curare-like manner. Neostigmine inhibits acetylcholinesterase and raises acetylcholine in the cleft, and atropine or glycopyrrolate is given to block the muscarinic effects. A trial is made in patients with persistent neurotoxicity while ventilatory support is kept ready.

Option by option

  • A. Pralidoxime with atropine

    Pralidoxime reactivates cholinesterase in organophosphate poisoning, and does not help in cobra bite.

  • B. Glycopyrrolate alone

    An antimuscarinic alone would not improve neuromuscular transmission.

  • C. Dantrolene alone

    Dantrolene acts on the sarcoplasmic reticulum and does not reverse the receptor block.

  • D. Neostigmine with atropine (correct)

    Correct. Increasing acetylcholine in the cleft can overcome the postsynaptic block.

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 Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is D, Neostigmine with atropine. Cobra neurotoxin acts at the postsynaptic acetylcholine receptors, in a curare-like manner.

Why is "Pralidoxime with atropine" not the answer?

Pralidoxime reactivates cholinesterase in organophosphate poisoning, and does not help in cobra bite.

Why is "Glycopyrrolate alone" not the answer?

An antimuscarinic alone would not improve neuromuscular transmission.

Why is "Dantrolene alone" not the answer?

Dantrolene acts on the sarcoplasmic reticulum and does not reverse the receptor block.

What concept does this question test?

It tests Toxicology: neostigmine in neurotoxic snakebite in Forensic Medicine. Neostigmine inhibits acetylcholinesterase and raises acetylcholine in the cleft, and atropine or glycopyrrolate is given to block the muscarinic effects. A trial is made in patients with persistent neurotoxicity while ventilatory support is kept ready.

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: neostigmine in neurotoxic snakebite?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine 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.