Pharmacokinetics and Optimal Timing of Dronedarone Initiation Following Long-term Amiodarone in Patients With Paroxysmal or Persistent Atrial Fibrillation

Inclusion criteria: Screening: * Paroxysmal or persistent AF having received at least 6 months of amiodarone before screening with at least the last 2 months at a regimen of 200 mg/day (during at least 5 days per week) prior to screening * Requiring a change from amiodarone treatment whatever the reason, but without liver, lung or thyroid toxicity related to previous use of amiodarone * At least one cardiovascular risk factor (i.e. age \> 70, hypertension, diabetes, prior cerebrovascular disease or left atrial diameter \>= 50 mm * Effective anticoagulation treatments verified by International Normalized Ratio (INR) (target INR \> 2) * QTc Bazett \< 500 ms on 12-lead ECG Randomization: * Outpatients and Inpatients (except patients hospitalized during screening period for SAE) * Sinus rhythm * Effective oral anticoagulation treatment verified by INR (target INR \> 2). INR should be closely monitored after initiating dronedarone in patients taking vitamin K antagonist as per their label * QTc Bazett \< 500 ms and PR \< 280 ms on 12-lead ECG Exclusion criteria: Screening: * Contraindication to oral anticoagulation * Acute condition known to cause AF * Permanent AF * Bradycardia \< 50 bpm at rest on the 12-lead ECG * History of, or current heart failure or left ventricular systolic dysfunction * Unstable hemodynamic conditions * Severe hepatic impairment * Wolff-Parkinson-White Syndrome * Previous catheter ablation for atrial fibrillation or catheter ablation scheduled in the next 10 weeks * Previous history of Amiodarone intolerance or toxicity * History of thyroid dysfunction * Mandatory contraindicated concomitant treatment: * potent cytochrome P450 (CYP3A4) inhibitors * drugs or herbal products that prolong the QT interval and known to increase the risk of Torsade de Pointes * Previous treatment with class I or class III anti-arrhythmic drugs (including sotalol) other than amiodarone if the anti-arrhythmic drug was taken less than one week before the day of screening (if taken more than one week before screening, the patient can be included) Randomization * Bradycardia \< 50 bpm on the 12-lead ECG * History of, or current heart failure or left ventricular systolic dysfunction * Unstable hemodynamic conditions * Severe hepatic impairment * Mandatory contraindicated concomitant treatment: * potent cytochrome P450 (CYP3A4) inhibitors * drugs or herbal products that prolong the QT interval and known to increase the risk of Torsade de Pointes The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.