**Core Concept**
Digitalis-induced ventricular arrhythmias are due to sodium channel blockade and delayed repolarization, leading to conduction abnormalities and instability. The treatment must rapidly stabilize the myocardium while avoiding worsening of digoxin toxicity or proarrhythmic effects.

**Why the Correct Answer is Right**
IV lignocaine (lidocaine) is the first-line agent for ventricular arrhythmias in patients with digitalis toxicity. It works by blocking cardiac sodium channels, particularly in ischemic or toxic states, thereby stabilizing the myocardial membrane potential. Unlike quinidine or procainamide, which can potentiate digoxin toxicity by inhibiting its metabolism or increasing cardiac conduction, lignocaine has minimal interaction with digoxin and is less likely to cause severe toxicity. It is also rapidly available intravenously and effective in terminating ventricular tachycardia.

**Why Each Wrong Option is Incorrect**
Option B: Phenytoin can be effective in some arrhythmias but has a high risk of causing digoxin toxicity due to reduced digoxin clearance and increased risk of bradycardia. It is not preferred in digitalis toxicity.
Option C: Quinidine is contraindicated in digitalis toxicity because it enhances digoxin’s cardiac effects, leading to severe arrhythmias including ventricular fibrillation.
Option D: Procainamide can also increase digoxin toxicity and has a higher risk of proarrhythmia in digitalis toxicity, making it unsuitable.

**Clinical Pearl / High-Yield Fact**
In digitalis-induced arrhythmias, **lignocaine is preferred over other antiarrhythmics** due to its safety profile and lack of interaction with digoxin. Always avoid quinidine and procainamide in such cases.

✓ Correct Answer: A. I.V. Lignocaine