Paper I — 2025 March (Supplementary (SAY)) (2019 Scheme) — Qxvii
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Paper I
2025 March (Supplementary (SAY)) (2019 Scheme) · 100 marks · 180 min
Question
Assertion (A): Quinidine can cause QT prolongation.
Reason (R): Class IA drugs have maximum sodium channel blocking effect.
Assertion) Quinidine can cause QT prolongation.
Reason) Class IA drugs have maximum sodium channel blocking effect.
a) Both A and R are true, and R is the correct explanation of A
c) A is true but R is false
b) Both A and R are true, and R is not the correct explanation of A
d) A is false but R is true
Qxvii1 marksMCQs (A/R)
Answer
Correct answer: c) A is true but R is false
A is true — quinidine (a Class IA antiarrhythmic) is well known to cause QT prolongation and can precipitate torsades de pointes. R is false: Class IA drugs have an intermediate degree of sodium channel blockade (Class IC drugs, such as flecainide, have the most potent/maximum Na⁺ channel blocking effect). Quinidine’s QT prolongation arises from its additional potassium channel-blocking action delaying repolarization, not from “maximum” sodium channel blockade.
