Amiodarone has been hailed as the most effective single antiarrhythmic drug for treatment of refractory supraventricular and ventricular arrhythmias. However, questions continue to arise about its long-term potential toxicity and true efficacy rates. We, therefore, reviewed our experience with 78 patients, mean age 59 +/- 14 years, with drug refractory tachyarrhythmias treated with amiodarone. Sixty-two patients were treated for recurrent ventricular tachycardia or ventricular fibrillation, 4 for complex ventricular ectopy and 12 for supraventricular tachyarrhythmias. Patients have been treated for a mean of 9.9 months (range, 1 day to 39.1 months); 34(55%) continued to be successfully treated for ventricular tachycardia/ventricular fibrillation, 2 (50%) for complex ventricular ectopy and 5 (42%) for supraventricular tachyarrhythmias. Amiodarone toxicity was frequent, occurring in 57/72 patients (79%) who were treated for more than one week. Adverse effects led to drug discontinuation in 15 (21%), 3 because of pulmonary toxicity (1 in combination with neuropathy and another with drug-induced hepatitis); 2 because of chemical hepatitis; 1, confusion; 6, neuropathy; 2, arrhythmia exacerbation; 2, symptomatic bradycardia; and 1 because of impotence. Of the 62 ventricular tachycardia/ventricular fibrillation patients who were treated with amiodarone, 8 (13%) expired: 4 died suddenly and 4 from documented ventricular tachycardia during treatment. In contrast, of 16 patients who had discontinued amiodarone because of initial adverse effects or drug failure and were treated with alternative antiarrhythmic medications, 5 (31%) died suddenly. In conclusion, amiodarone appears to be fairly effective in high risk patients with refractory cardiac tachyarrhythmias but results in a rather high incidence of adverse effects in long-term follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)