An ANTIARRHYTHMIC DRUG given by intravenous injection after myocardial infarction to restore supraventricular and ventricular arrhythmias to normal, particularly when patients have not responded to lidocaine (lignocaine). It can impair the contractility of heart muscle and it does have an ANTIMUSCARINIC effect; consequently its administration has to be undertaken with care, especially in patients with GLAUCOMA or cardiac enlargement.