Paper I — 2024 December (Supplementary) (2019 Scheme) — Qxviii
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Paper I
2024 December (Supplementary) (2019 Scheme) · 100 marks · 180 min
Question
Assertion (A): Lignocaine is one of the preferred drugs in paroxysmal supraventricular
tachycardia.
Reason (R): Lignocaine is a blocker of inactivated Na+ channels more than that of open
state. It is relatively selective for partially depolarized cells and those with longer action
potential duration.
a) Both A and R are true, and R is the correct explanation of A
b) Both A and R are true, and R is not the correct explanation of A
c) A is true, but R is false
d) A is false, but R is true
(PTO)
Qxviii1 marksMCQs
Answer
Correct answer: d) A is false, but R is true
(PTO)
A is false — lignocaine is a Class IB antiarrhythmic used for ventricular arrhythmias (particularly post-myocardial infarction), not paroxysmal supraventricular tachycardia. R is a true, accurate description of lignocaine’s mechanism: it preferentially blocks inactivated Na⁺ channels, giving it selectivity for partially depolarized (ischemic) tissue and cells with longer action potential duration — this mechanism explains its ventricular-arrhythmia selectivity, not an SVT indication.
