Match the following Class and their Antiarrhythmic Drug:
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The Vaughan Williams classification helps in identifying antiarrhythmic agents by their primary mechanism and is essential in managing arrhythmias effectively.
Antiarrhythmic drugs are classified based on the Vaughan Williams classification system into four main classes according to their primary mechanism of action:
\begin{itemize}
\item Class I – Sodium channel blockers. These drugs reduce the rate of rise of phase 0 of the action potential. Disopyramide, a Class Ia agent, falls under this category. (1)-(P)
\item Class II – Beta-adrenergic blockers. These reduce sympathetic activity, decrease heart rate, and conduction velocity. Metoprolol is a selective beta-1 blocker. (2)-(Q)
\item Class III – Potassium channel blockers. These prolong repolarization and the action potential duration. Amiodarone is a prototype agent. (3)-(R)
\item Class IV – Calcium channel blockers. These affect the SA and AV nodes, reducing conduction velocity. Verapamil is a non-dihydropyridine calcium channel blocker. (4)-(S)
\end{itemize}
Matching accordingly:
- (1)-(P) Disopyramide
- (2)-(Q) Metoprolol
- (3)-(R) Amiodarone
- (4)-(S) Verapamil
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Approach Solution -2
This question asks you to match four classes of antiarrhythmic drugs, based on the Vaughan Williams classification, with representative drugs from list II. Before checking the four answer choices, fix the drug-class pairing itself: Class I (sodium channel blockers) is represented by Disopyramide (P), Class II (beta blockers) by Metoprolol (Q), Class III (potassium channel blockers) by Amiodarone (R), and Class IV (calcium channel blockers) by Verapamil (S). Now check each option against this pairing.
(1)-(P), (2)-(Q), (3)-(R), (4)-(S): This places Disopyramide with Class I, Metoprolol with Class II, Amiodarone with Class III, and Verapamil with Class IV. Every pair matches the mechanism of the drug, so this combination is correct.
(1)-(Q), (2)-(R), (3)-(S), (4)-(P): This puts Metoprolol, a beta blocker, against Class I and Disopyramide, a sodium channel blocker, against Class IV. Neither drug's mechanism fits the class it is paired with, so this combination is wrong.
(1)-(R), (2)-(Q), (3)-(P), (4)-(S): Here Amiodarone, a potassium channel blocker, is placed against Class I, and Disopyramide, a sodium channel blocker, is placed against Class III. Both pairs mismatch the drug's actual mechanism, so this combination is wrong.
(1)-(Q), (2)-(R), (3)-(P), (4)-(S): This pairs Metoprolol with Class I and Amiodarone with Class II, again crossing drugs into classes their mechanism does not belong to, so this combination is wrong.
Only the first combination lines up every drug with the class matching its actual mechanism of action.
Therefore, the correct answer is (1)-(P), (2)-(Q), (3)-(R), (4)-(S).
