In one US multicenter study (Rythmol SR Atrial Fibrillation Trial, RAFT), 3 doses of RYTHMOL SR (225 mg twice daily, 325 mg twice daily and 425 mg twice daily) and placebo were compared in 523 patients with symptomatic, episodic atrial fibrillation. The patient population in this trial was 59% male with a mean age of 63 years, 91% white and 6% black. The patients had a median history of atrial fibrillation of 13 months, and documented symptomatic atrial fibrillation within 12 months of study entry.