Description: Mexiletine is a Class Ib antiarrhythmic drug. It is an oral medication structurally similar to lidocaine and is used to treat serious abnormal heart rhythms.

Indications: Mexiletine is primarily used to treat documented life-threatening ventricular arrhythmias, such as sustained ventricular tachycardia. It is also used in some cases to treat chronic pain, including diabetic neuropathy, and muscle stiffness associated with myotonic disorders.

Mechanism of Action: Mexiletine works by blocking fast inward sodium channels in the heart’s nerve cells. This action inhibits the inward sodium current, which is responsible for the initial rapid rise (Phase 0) of the action potential. By doing so, it stabilizes the heart’s electrical signals and helps to correct irregular heartbeats. This drug has fast onset and offset kinetics, meaning its effect is more pronounced at faster heart rates.