Amiodarone and its infusion velocity in recent-onset atrial fibrillation]

Two intravenous amiodarone dosing schedules in 28 patients with atrial fibrillation arisen less than 10 days before, were evaluated. Their effectiveness in converting to sinus rhythm, the incidence of side effects and the relationship between efficacy and plasma concentrations of amiodarone and desethylamiodarone were compared. Schedule A, with amiodarone infusion at a rate of 1.5 mg/kg/h up to two hours after the restoration of sinus rhythm or to a maximum dose of 1200 mg, reverted 86.7% of all patients. Schedule B, with a single amiodarone infusion of 300 mg over 15 minutes, followed by a 300 mg dose maintenance over three hours, reverted 69.2% of all patients. Schedule A was more effective than schedule B (P less than 0.01). Schedule B reverted before A (P less than 0.05). The only transient adverse effects were: superficial phlebitis, symptomatic hypotension and silent QTc lengthening. Amiodarone and desethylamiodarone plasma concentrations were not related to efficacy of the drug in converting sinus rhythm. In conclusion, an intravenous infusion of amiodarone over few hours showed high efficacy (79.6%), wide therapeutic index, good compliance and irrelevant adverse effects in converting patients with recent-onset fibrillation.