Autonomic: pralidoxime and carbamates: 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 · Autonomic: pralidoxime and carbamates

Sample item

A farm worker is poisoned with carbaryl, a carbamate insecticide, and has mild cholinergic features. Why is pralidoxime generally not needed?

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

The answer and the reasoning

A. Carbamate inhibition of cholinesterase is spontaneously reversible, and there is no aged phosphorylated enzyme to reactivate

Carbamylated cholinesterase regenerates spontaneously within hours, so oximes are usually unnecessary, and some data suggest possible harm with carbaryl. Atropine remains the mainstay for muscarinic symptoms. Pralidoxime is valuable in organophosphate poisoning before ageing.

Option by option

  • A. Carbamate inhibition of cholinesterase is spontaneously reversible, and there is no aged phosphorylated enzyme to reactivate (correct)

    Correct. Carbamate inhibition is short lived and reversible.

  • B. Pralidoxime is only effective if given after 48 hours

    Oximes work best early, before enzyme ageing, not after 48 hours.

  • C. Pralidoxime worsens carbamate toxicity by crossing the blood-brain barrier

    Pralidoxime does not cross the blood-brain barrier well and is not contraindicated for that reason.

  • D. Carbamates act on muscarinic receptors directly

    Carbamates inhibit cholinesterase rather than directly activating receptors.

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, Carbamate inhibition of cholinesterase is spontaneously reversible, and there is no aged phosphorylated enzyme to reactivate. Carbamylated cholinesterase regenerates spontaneously within hours, so oximes are usually unnecessary, and some data suggest possible harm with carbaryl.

Why is "Pralidoxime is only effective if given after 48 hours" not the answer?

Oximes work best early, before enzyme ageing, not after 48 hours.

Why is "Pralidoxime worsens carbamate toxicity by crossing the blood-brain ba…" not the answer?

Pralidoxime does not cross the blood-brain barrier well and is not contraindicated for that reason.

Why is "Carbamates act on muscarinic receptors directly" not the answer?

Carbamates inhibit cholinesterase rather than directly activating receptors.

What concept does this question test?

It tests Autonomic: pralidoxime and carbamates in Pharmacology. Atropine remains the mainstay for muscarinic symptoms. Pralidoxime is valuable in organophosphate poisoning before ageing.

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 Autonomic: pralidoxime and carbamates?

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.