Tocainide is a primary amine analog of lidocaine with antiarrhythmic properties useful in the treatment of ventricular arrhythmias. Tocainide, like lidocaine, produces dose-dependent decreases in sodium and potassium conductance, thereby decreasing the excitability of myocardial cells. In experimental animal models, the dose-related depression of sodium current is more pronounced in ischemic tissue than in normal tissue. Tocainide is a Class I antiarrhythmic compound with electrophysiologic properties in man similar to those of lidocaine, but dissimilar from quinidine, procainamide, and disopyramide. The recommended initial dosage is 400 mg every 8 hours. The usual adult dosage is between 1200 and 1800 mg/day in a three-dose daily divided regimen. Doses beyond 2400 mg per day have been administered infrequently. Patients who tolerate the t.i.d. the regimen may be tried on a twice-daily regimen with careful monitoring. Tocainide commonly produces minor, transient, nervous system and gastrointestinal adverse reactions, but is otherwise generally well tolerated.