Mexiletine is a class 1B, sodium channel blocker, anti-arrhythmia drug which is used to treat chronic ventricular arrhythmias in dogs. The mechanism of action is similar to lidocaine. Mexiletine is used to treat ventricular arrhythmias including PVC’s and ventricular tachycardia. If an animal has responded well to lidocaine during an acute episode, it is likely to respond well to Mexiletine. Mexiletine may be used to treat inherited cardiomyopathy in Boxers and dilated cardiomyopathy in Doberman pinschers.