Tocainide. A review of its pharmacological properties and therapeutic efficacy.

Tocainide is an antiarrhythmic drug structurally related to lignocaine with similar electrophysiological, haemodynamic and antiarrhythmic effects. In contrast to lignocaine (lidocaine) it is well absorbed after oral administration and has a plasma half-life of about 15 hours. In several open and controlled therapeutic trials in patients with ventricular arrhythmias, often following a myocardial infarction, tocainide has been relatively effective and usually well tolerated. In treating ventricular ectopic beats and/or ventricular tachycardia tocainide has demonstrated effective suppression in 60 to 70% of patients in both open and controlled studies. It has an acute effect when infused in patients with ventricular arrhythmias complicating myocardial infarction, as well as a prophylactic effect when given orally. The majority of these studies have demonstrated tocainide to be more effective than placebo, but trials against other antiarrhythmic agents are few in number and vary in design. One study combining an infusion of tocainide with oral therapy compared to a bolus injection of lignocaine followed by a constant infusion in patients after myocardial infarction, found the two agents to be of similar efficacy. The most common adverse effects are neurological and gastrointestinal in nature, nausea and dizziness occurring most frequently. Adverse effects resulting in termination of therapy have been reported in about 16% of patients. Aggravation of pre-existing heart failure, increased ventricular arrhythmia, deterioration of conduction disturbances, convulsions, and cases of lupus erythematosus syndrome have occasionally been reported. Thus, tocainide appears to offer a worthwhile addition to the other antiarrhythmic agents available for ventricular arrhythmias. However, its relative place in therapy compared with other antiarrhythmic drugs is not yet clearly established.