Anaesthetic pharmacology: curriculum recognition: 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 · Anaesthetic pharmacology: curriculum recognition

Sample item

Compared with lignocaine, bupivacaine and ropivacaine produce longer-lasting blocks. Which property is chiefly responsible for the longer duration of action?

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

The answer and the reasoning

C. Degree of protein binding

Duration of action of local anaesthetics correlates with protein binding, because highly bound drugs remain at the nerve membrane receptor sites and leave slowly. The pKa mainly affects onset of action.

Option by option

  • A. Water solubility

    Water solubility does not determine how long the drug acts.

  • B. pKa

    The pKa determines the fraction unionised and so mainly the onset.

  • C. Degree of protein binding (correct)

    Correct. High protein binding prolongs duration.

  • D. Ester linkage

    An ester linkage is hydrolysed rapidly by plasma cholinesterase and shortens duration.

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 C, Degree of protein binding. Duration of action of local anaesthetics correlates with protein binding, because highly bound drugs remain at the nerve membrane receptor sites and leave slowly.

Why is "Water solubility" not the answer?

Water solubility does not determine how long the drug acts.

Why is "pKa" not the answer?

The pKa determines the fraction unionised and so mainly the onset.

Why is "Ester linkage" not the answer?

An ester linkage is hydrolysed rapidly by plasma cholinesterase and shortens duration.

What concept does this question test?

It tests Anaesthetic pharmacology: curriculum recognition in Anaesthesia. The pKa mainly affects onset of action.

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 Anaesthetic pharmacology: curriculum recognition?

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.