Local anaesthetics: mechanism: 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 · Local anaesthetics: mechanism

Sample item

Local anaesthetics block nerve conduction mainly by which mechanism?

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

The answer and the reasoning

C. Binding the inner pore of voltage-gated sodium channels in their ionised form

The unionised form crosses the membrane, and the ionised form binds within the sodium channel to block conduction, with use-dependent block of rapidly firing fibres. Infected tissue is acidic, so less drug is unionised and the effect is reduced.

Option by option

  • A. Activating GABA receptors

    GABA action is not involved.

  • B. Blocking calcium channels at the terminal

    Calcium channel block is not the main action.

  • C. Binding the inner pore of voltage-gated sodium channels in their ionised form (correct)

    Correct. Sodium channel block by the ionised form is the mechanism.

  • D. Opening potassium channels

    Potassium channel opening 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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, Binding the inner pore of voltage-gated sodium channels in their ionised form. The unionised form crosses the membrane, and the ionised form binds within the sodium channel to block conduction, with use-dependent block of rapidly firing fibres.

Why is "Activating GABA receptors" not the answer?

GABA action is not involved.

Why is "Blocking calcium channels at the terminal" not the answer?

Calcium channel block is not the main action.

Why is "Opening potassium channels" not the answer?

Potassium channel opening is not the mechanism.

What concept does this question test?

It tests Local anaesthetics: mechanism in Pharmacology. Infected tissue is acidic, so less drug is unionised and the effect is reduced.

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: mechanism?

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.