It is a class 3 antiarrhythmic drug.

Indications: treatment of arrhythmias when other antiarrhythmic drugs are contraindicated or ineffective; supraventricular and ventricular tachycardias, atrial fibrillation and flutter and ventricular fibrillation. Also for tachyarrhythmias associated with Wolff-Parkinson-White syndrome.

Cautions: sinus bradycardia, heart block unless pacemaker is fitted; avoid in severe conduction defects or sinus node disease, cardiomyopathy and heart failure.

Liver and thyroid functions should be checked before and during long term therapy. Regular eye examination during long term therapy (Treatment should be initiated in a hospital or under specialist supervision).

Contra-indications: sinus bradycardia, sino-atrial block, thyroid dysfunction, iodine sensitivity.

Side Effects: nausea, vomiting, raised serum transaminases, jaundice, bradycardia, thyroid dysfunction, corneal opacity, photosensitivity and skin discolouration; circulatory collapse can occur with rapid IV injection.

Dose: by mouth, 200 mg 3 times daily for 1 week reduced to 200 mg twice daily for a further week. Maintenance, usually 200 mg daily or the minimum required to control the arrhythmias.

By l.V. infusion via central catheter, up to 5 mg/kg over 20-120 minutes with ECG and blood pressure monitoring; max. 1.2 g in 24 hours.