Which medication can be used as a local anesthetic and as a first-line anti-arrhythmic for treating acute life-threatening ventricular arrhythmia?

The medication that serves both as a local anesthetic and as a first-line anti-arrhythmic for treating acute life-threatening ventricular arrhythmia is Lidocaine. Known scientifically as a class 1B antiarrhythmic agent, Lidocaine effectively stabilizes myocardial membranes and decreases automaticity. This makes it particularly useful in acute situations like ventricular tachycardia or ventricular fibrillation, where rapid intervention is essential to restore normal heart rhythm.

Lidocaine's ability to block sodium channels helps to prevent the abnormal electrical signals that cause arrhythmias from propagating through the heart tissue. Its rapid onset and relatively short duration of action make it ideal for emergency settings. While Xylocaine is a brand name for Lidocaine, it's important to recognize that the question refers specifically to the broader category of Lidocaine as the correct answer, highlighting its dual role in both local anesthesia and cardiac rhythm management.

The other medications, like Procaine and Bupivacaine, are primarily used as local anesthetics with different profiles and applications and do not possess the same properties for treating life-threatening ventricular arrhythmias.