Which class of antiarrhythmic is lidocaine categorized under?

Lidocaine is categorized as a Class IB antiarrhythmic agent. This classification system for antiarrhythmic medications is based on their effects on cardiac action potentials and their mechanism of action.

Class IB agents primarily work by blocking sodium channels during phase 0 of the cardiac action potential, but they have a more pronounced effect on depolarized or ischemic tissue compared to normal tissue. This characteristic makes them particularly effective in managing certain types of ventricular arrhythmias, including those that occur after myocardial infarction. Lidocaine's rapid onset and short duration of action also support its use in acute situations, such as during cardiac emergencies.

In distinguishing characteristics within the antiarrhythmic classes, Class IA agents, for example, have a moderate effect on sodium channels and additionally block potassium channels, while Class IC agents have a stronger sodium channel blockade but affect conduction velocity. Class II agents, on the other hand, are primarily beta-blockers that decrease heart rate and have a different mechanism of action compared to lidocaine.

Therefore, the classification of lidocaine as a Class IB antiarrhythmic is based on its sodium channel blocking properties and its specific clinical use in treating ventricular arrhythmias.