Long term efficacy and toxicity of amiodarone in the treatment of refractory cardiac arrhythmias.

Amiodarone has remarkable efficacy, but it also has a high incidence of severe side effects. Nevertheless, it is extensively used. The findings of an amiodarone treatment follow-up period of one to 72 months (mean 19 +/- 17) in 95 patients with recurrent life threatening arrhythmias resistant to other antiarrhythmic drugs are described. The mean loading dose of 800 mg/day for one week was followed by an average dose of 600 mg/day for two weeks. The long term daily dose was 400 mg in 80 patients and 200 mg in the remaining 15 patients. Amiodarone was particularly effective in suppressing complex ventricular arrhythmias. It also decreased premature ventricular beats by 83% and atrial premature beats by 41%. Supraventricular tachycardias were completely controlled and the ventricular response to atrial fibrillation was slowed. Twelve of the 95 patients (12.6%) died while taking amiodarone, two of sudden death and 10 of heart failure. Side effects were recorded in 77 (81%) patients. They were generally dose related and subsided with a decrease in dose or discontinuation of the medication. There was a correlation between the concentration of rT3 and the significance of the side effects. Thirty-nine patients stopped taking amiodarone, however, only 14 of these stopped because of toxicity: five developed pulmonary fibrosis; three had neurological toxicity; two had bradyarrhythmias; two developed hepatic dysfunction; one had hypothyroidism; and one patient suffered an aggravation of a pre-existent heart failure. It was concluded that amiodarone is a very effective treatment for supraventricular and ventricular arrhythmias. However, it does have numerous and severe side effects.(ABSTRACT TRUNCATED AT 250 WORDS)