Cardiovascular drugs: lidocaine state dependence: 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: lidocaine state dependence

Sample item

Lidocaine suppresses ventricular tachycardia from ischaemic myocardium but has little effect on atrial arrhythmias. Which property best explains this selectivity?

AStimulation of muscarinic receptors in the atriaBPreferential binding to inactivated sodium channelsCProlongation of action potential duration in atriaDBlock of L-type calcium channels in nodal tissue

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

The answer and the reasoning

B. Preferential binding to inactivated sodium channels

Lidocaine, a class IB drug, binds mainly to inactivated sodium channels and dissociates rapidly. Ischaemic ventricular tissue is depolarised and fires rapidly, so many channels are inactivated, while the short atrial action potential leaves few channels in that state.

Option by option

A. Stimulation of muscarinic receptors in the atria
Lidocaine does not stimulate muscarinic receptors.
B. Preferential binding to inactivated sodium channels (correct)
Correct. Depolarised ischaemic cells have more inactivated channels for lidocaine to bind.
C. Prolongation of action potential duration in atria
Class IB drugs shorten rather than prolong the action potential.
D. Block of L-type calcium channels in nodal tissue
Lidocaine has no clinically relevant calcium channel blocking action in nodal tissue.

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.

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, Preferential binding to inactivated sodium channels. Lidocaine, a class IB drug, binds mainly to inactivated sodium channels and dissociates rapidly.

Why is "Stimulation of muscarinic receptors in the atria" not the answer?

Lidocaine does not stimulate muscarinic receptors.

Why is "Prolongation of action potential duration in atria" not the answer?

Class IB drugs shorten rather than prolong the action potential.

Why is "Block of L-type calcium channels in nodal tissue" not the answer?

Lidocaine has no clinically relevant calcium channel blocking action in nodal tissue.

What concept does this question test?

It tests Cardiovascular drugs: lidocaine state dependence in Pharmacology. Ischaemic ventricular tissue is depolarised and fires rapidly, so many channels are inactivated, while the short atrial action potential leaves few channels in that state.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: lidocaine state dependence?

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.