Local anaesthetics: ester allergy: practice question

A Anaesthesia 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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Anaesthesia · Local anaesthetics: ester allergy

Sample item

Why are ester local anaesthetics more likely to cause allergic reactions than amides?

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

The answer and the reasoning

B. Their metabolite para-aminobenzoic acid is allergenic

Ester hydrolysis releases PABA, which is a recognised hapten. True allergy to amides is rare and is usually due to preservatives such as methylparaben.

Option by option

  • A. They contain sulphites only

    Sulphites are a different issue.

  • B. Their metabolite para-aminobenzoic acid is allergenic (correct)

    Correct. PABA is the allergen.

  • C. They are metabolised in the liver

    Hepatic metabolism applies to amides.

  • D. They release histamine directly at injection

    Histamine release is not the mechanism.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is B, Their metabolite para-aminobenzoic acid is allergenic. Ester hydrolysis releases PABA, which is a recognised hapten.

Why is "They contain sulphites only" not the answer?

Sulphites are a different issue.

Why is "They are metabolised in the liver" not the answer?

Hepatic metabolism applies to amides.

Why is "They release histamine directly at injection" not the answer?

Histamine release is not the mechanism.

What concept does this question test?

It tests Local anaesthetics: ester allergy in Anaesthesia. True allergy to amides is rare and is usually due to preservatives such as methylparaben.

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 Local anaesthetics: ester allergy?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia 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.