Question:medium
Q-T prolongation is most characteristically seen with which drug?
Q-T prolongation is most characteristically seen with which drug?
Show Hint
Which class IA antiarrhythmic is the classic cause of Torsades de Pointes?
Updated On: Jun 24, 2026
- Quinidine
- Amiodarone
- Magnesium sulfate
- Lignocaine
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: QT prolongation reflects delayed ventricular repolarization, usually from blockade of the rapid delayed-rectifier potassium current.
Step 2: Quinidine, a class IA drug, is the textbook offender; the resulting polymorphic ventricular tachycardia is named Torsades de Pointes, and quinidine heads the list of culprit drugs.
Step 3: Lignocaine works oppositely (class IB shortens the action potential), and magnesium sulfate is the antidote given to suppress Torsades rather than cause it.
Step 4: So the single best answer for marked QT prolongation is quinidine.
\[\boxed{\text{Quinidine}}\]
Step 2: Quinidine, a class IA drug, is the textbook offender; the resulting polymorphic ventricular tachycardia is named Torsades de Pointes, and quinidine heads the list of culprit drugs.
Step 3: Lignocaine works oppositely (class IB shortens the action potential), and magnesium sulfate is the antidote given to suppress Torsades rather than cause it.
Step 4: So the single best answer for marked QT prolongation is quinidine.
\[\boxed{\text{Quinidine}}\]
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