Cardiovascular drugs: lignocaine selectivity: 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 · Cardiovascular drugs: lignocaine selectivity

Sample item

A 55-year-old man with an anterior myocardial infarction has sustained ventricular tachycardia and is given intravenous lignocaine. Why is it more effective in ischaemic myocardium than in healthy tissue?

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

The answer and the reasoning

B. It binds preferentially to open and inactivated sodium channels, which are more frequent in depolarised tissue

Lignocaine is a class IB agent with fast on-off kinetics. It binds open and inactivated sodium channels, and ischaemic cells are partially depolarised so that many channels sit in the inactivated state. Hence it suppresses arrhythmias from diseased tissue with little effect on normal conduction, and it shortens the action potential.

Option by option

  • A. It blocks L-type calcium channels that are overactive in ischaemia

    Calcium channel blockade is the action of verapamil and diltiazem, not lignocaine.

  • B. It binds preferentially to open and inactivated sodium channels, which are more frequent in depolarised tissue (correct)

    Correct. State-dependent binding gives selectivity for abnormal, depolarised myocardium.

  • C. It blocks potassium channels and prolongs the action potential in ischaemic cells

    Class III agents such as amiodarone block potassium channels; lignocaine shortens rather than prolongs the action potential.

  • D. It blocks beta-1 receptors that are upregulated in ischaemic cells

    Beta-blockade is the action of drugs such as esmolol, not lignocaine.

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.

More Pharmacology questions

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, It binds preferentially to open and inactivated sodium channels, which are more frequent in depolarised tissue. Lignocaine is a class IB agent with fast on-off kinetics.

Why is "It blocks L-type calcium channels that are overactive in ischaemia" not the answer?

Calcium channel blockade is the action of verapamil and diltiazem, not lignocaine.

Why is "It blocks potassium channels and prolongs the action potential in isc…" not the answer?

Class III agents such as amiodarone block potassium channels; lignocaine shortens rather than prolongs the action potential.

Why is "It blocks beta-1 receptors that are upregulated in ischaemic cells" not the answer?

Beta-blockade is the action of drugs such as esmolol, not lignocaine.

What concept does this question test?

It tests Cardiovascular drugs: lignocaine selectivity in Pharmacology. It binds open and inactivated sodium channels, and ischaemic cells are partially depolarised so that many channels sit in the inactivated state. Hence it suppresses arrhythmias from diseased tissue with little effect on normal conduction, and it shortens the action potential.

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 Cardiovascular drugs: lignocaine selectivity?

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.