Rapid control of refractory atrial tachyarrhythmias with high-dose oral amiodarone. To shorten the delay in the onset of antiarrhythmic effect when using amiodarone for the conversion of refractory atrial tachyarrhythmias to sinus rhythm, 19 patients were given oral amiodarone according to a high-dose loading protocol. In 18 of 19 patients (95%), sinus rhythm was restored 36 hours (range, 0 to 96 hours) after starting amiodarone. The conversion occurred as a result of amiodarone therapy alone within 48 hours in 12 patients (63%), and by amiodarone therapy plus electrical cardioversion at 48 to 96 hours in six patients (32%). Minor side effects were noted in eight patients (42%). No major side effects were encountered. The length of hospital stay after initiating amiodarone therapy was 3.6 days (range, 2 to 5 days). High-dose oral amiodarone loading is a safe and effective method for the rapid conversion of atrial tachyarrhythmias to sinus rhythm. 