Question

Which of the following is NOT a Class 1C anti-arrhythmic drug:

• A. \( \text{Propafenone} \)
• B. \( \text{Mexiletine} \)
• C. \( \text{Flecainide} \)
• D. \( \text{Moricizine} \)

Hint:

Anti-arrhythmic drugs are classified into four main classes based on the Vaughan-Williams classification. Class 1 drugs (sodium channel blockers) are further divided into: 
- 1A: Moderate sodium blockade (e.g., Quinidine). 
- 1B: Weak sodium blockade (e.g., Mexiletine). 
- 1C: Strong sodium blockade (e.g., Flecainide, Propafenone).

Answer 1

The Correct Option is B

Step 1: Understanding Class 1C anti-arrhythmic drugs. Class 1C anti-arrhythmic drugs are sodium channel blockers with a strong effect on the cardiac action potential. They are used to manage arrhythmias by slowing conduction and reducing automaticity in the heart. Examples include: - \( \text{Propafenone} \), - \( \text{Flecainide} \), - \( \text{Moricizine} \). 

Step 2: Differentiating Mexiletine. Mexiletine is a Class 1B anti-arrhythmic drug, not Class 1C. Class 1B drugs have a weaker effect on the sodium channels and are used for treating ventricular arrhythmias. 

Step 3: Comparison with other options. - Option \( (A) \): Propafenone is a Class 1C drug. 
- Option \( (C) \): Flecainide is a Class 1C drug. 
- Option \( (D) \): Moricizine is also a Class 1C drug. 

Conclusion: Mexiletine, a Class 1B drug, is the correct answer for NOT being a Class 1C anti-arrhythmic.