Cardiovascular: class IA antiarrhythmics: 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: class IA antiarrhythmics

Sample item

Class IA antiarrhythmic drugs such as quinidine and procainamide have which effect on the action potential?

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

The answer and the reasoning

A. Prolong action potential duration and QT interval with moderate sodium channel block

Class IA drugs block sodium channels with intermediate kinetics and also block potassium channels, thereby lengthening action potential duration and the QT interval, which may cause torsades de pointes. Class IB shorten it and class IC do not change it.

Option by option

  • A. Prolong action potential duration and QT interval with moderate sodium channel block (correct)

    Correct. IA drugs prolong repolarisation.

  • B. Have no effect on repolarisation

    They clearly affect repolarisation.

  • C. Block only calcium channels

    Calcium channel block describes class IV.

  • D. Shorten the action potential duration

    Shortening is a feature of class IB drugs.

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 A, Prolong action potential duration and QT interval with moderate sodium channel block. Class IA drugs block sodium channels with intermediate kinetics and also block potassium channels, thereby lengthening action potential duration and the QT interval, which may cause torsades de pointes.

Why is "Have no effect on repolarisation" not the answer?

They clearly affect repolarisation.

Why is "Block only calcium channels" not the answer?

Calcium channel block describes class IV.

Why is "Shorten the action potential duration" not the answer?

Shortening is a feature of class IB drugs.

What concept does this question test?

It tests Cardiovascular: class IA antiarrhythmics in Pharmacology. Class IB shorten it and class IC do not change it.

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: class IA antiarrhythmics?

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.