ACUTE TREATMENT OF RECENT-ONSET ATRIAL-FIBRILLATION AND FLUTTER WITH A TAILORED DOSING REGIMEN OF INTRAVENOUS AMIODARONE - A RANDOMIZED, DIGOXIN-CONTROLLED STUDY

A 24 h intravenous dosing regimen of amiodarone was designed to reach a peak plasma concentration at 1 h and to maintain the concentration a bove a certain level during the infusion period. A randomized, open-la bel, digoxin-controlled study was undertaken to observe the efficacy a nd safety of the dosing regimen of amiodarone in treating recent-onset , persistent atrial fibrillation and flutter with ventricular rates ab ove 130 beats . min(-1). Fifty patients with a mean age of 70 +/- 7 (S D) years were enrolled and randomly assigned to receive either amiodar one intravenously (n=26) or digoxin (n=24). Amiodarone HCl was infused over 24 it according to the following regimen: 5 mg . min(-1) 3 mg . min(-1), 1 mg . min(-1) and 0.5 mg . min(-1) for 1, 3, 6 and 14 h, res pectively, for a 70-kg subject. Digoxin (0.013 mg . kg(-1)) was infuse d in three divided doses, each dose 2 h apart and infused over 30 min. The mean heart rates in the amiodarone group decreased significantly from 157 +/- 20 beats . min(-1) to 122 +/- 25 beats . min(-1) after 1 h (P<0.05 vs baseline), and then decreased further to stabilize at 96 +/- 25 beats . min(-1) after 6 h (P<0.05). The digoxin group had fewer dramatic alterations in heart rates, compared to the amiodarone group , in the first 8 h (P<0.05, respectively). Maximum reduction was reach ed only after gh. The amiodarone infusion was prematurely aborted in t wo patients due to severe bradycardia and death after conversion in on e patient and aggravation of heart failure in the other. Overall, 24 o f 26 patients (92%) in the amiodarone group and 17 of 24 (71%) in the digoxin group were restored to sinus rhythm within 24 h. The accumulat ed rates of conversion over 24 h were significantly different between the two groups (P=0.0048). Digoxin, while not as effective as amiodaro ne in the treatment of recent-onset atrial fibrillation amd flutter, a ppears to be safer. Therefore, we suggest the use of digoxin as the fi rst line drug for the type of patients that formed the basis of the cu rrent study and reserve amiodarone for refractory cases or those in wh om digoxin is not suitable.