Question
An investigator is comparing the risk of adverse effects among various antiarrhythmic medications. One of the drugs being studied primarily acts by blocking the outward flow of K+ during myocyte repolarization. Further investigation shows that the use of this drug is associated with a lower rate of ventricular tachycardia, ventricular fibrillation, and torsade de points when compared to similar drugs. Which of the following drugs is most likely being studied?
| A. |
Sotalol
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| B. |
Procainamide
|
| C. |
Verapamil
|
| D. |
Amiodarone
|
Show Answer
|
Correct Answer � D
Explanation
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|
Ans-D-Amiodarone
Sotalol
Sotalol is a nonselective beta blocker with potent class II and class III antiarrhythmic properties. It is used in the treatment of supraventricular arrhythmias and ventricular arrhythmias. Like the drug being investigated, sotalol can also block potassium channels during myocyte repolarization, prolonging the action potential duration and effective refractory period. Unlike the drug being studied, sotalol has high arrhythmogenic potential and carries a high risk of inducing ventricular arrhythmias, such as torsades de pointes.
Procainamide
Procainamide is a class IA antiarrhythmic drug that primarily acts by blocking fast sodium channels. It can be used to treat paroxysmal supraventricular tachycardia, atrial fibrillation, atrial flutter, and ventricular tachycardia. Like the drug being investigated, procainamide can prolong the action potential duration and effective refractory period, but it has no effect on potassium channel blockade.
Verapamil
Verapamil is a nondihydropyridine calcium channel blocker with class IV antiarrhythmic drug properties. Class IV antiarrhythmic drugs prolong the repolarization of the AV node and can increase effective refractory periods. They are used in the treatment of paroxysmal supraventricular tachycardia, atrial fibrillation, atrial flutter, and multifocal atrial tachycardia. Unlike the drug under investigation, verapamil has no effect on potassium channels.
Amiodarone
Amiodarone (a class III antiarrhythmic drug) acts primarily by blocking outward potassium channels during myocyte repolarization, in addition to blocking sodium and calcium channels. Class III antiarrhythmic drugs prolong the action potential duration (APD) and effective refractory period (ERP), with no delay in conduction velocity. Like other class III agents, amiodarone can cause QT prolongation, although it carries a much lower risk of arrhythmia and torsades de pointes than other drugs of the same class.
