Question

Q-T elongation is seen in which drug?

• A. Quinidine
• B. Amiodarone
• C. Magnesium Sulfate
• D. Lignocaine

Answer 1

The Correct Option is A

To understand the concept of QT elongation and identify which drug is associated with it, we must first define what QT elongation means in pharmacology. The QT interval is a measure on the electrocardiogram (ECG) that reflects the time it takes for the heart's ventricles to depolarize and then repolarize. Prolongation of the QT interval can lead to dangerous arrhythmias.

Factors Contributing to QT Prolongation: Several drugs can cause QT prolongation, and the mechanism typically involves the blockade of cardiac potassium channels, specifically the delayed rectifier potassium current (I_Kr), which is crucial for cardiac repolarization.

Now, examining the drugs listed:

• Quinidine: Known as a Class IA antiarrhythmic, Quinidine works by inhibiting sodium and potassium channels, thereby prolonging the action potential duration and QT interval.
• Amiodarone: Although an antiarrhythmic that can also cause QT prolongation, it does so less markedly than Quinidine and has a low risk of causing Torsades de Pointes.
• Magnesium Sulfate: Typically used to treat certain types of arrhythmias, particularly those related to torsades de pointes, it does not cause QT elongation.
• Lignocaine (Lidocaine): This is a Class IB antiarrhythmic that does not appreciably prolong QT interval.

Considering the options and mechanisms, the correct answer is Quinidine, as it is the classic example of a drug that causes QT interval elongation.