In their search for a safe and effective antiarrhythmic drugs, pharmaceutical companies have long imagined their "Holy Grail:" a drug that is as effective as amiodarone, but without its unique toxicity. (Click here for a quick review of amiodarone.) Most lately, hopes had been high for the new antiarrhythmic drug dronedarone (Sanofi). Recently, the results of two clinical trials with dronedarone were reported. Investigators from these trials conclude that dronedarone is effective and has a favorable safety profile - yet, the results can only be considered disappointing.
In these trials, over 1200 patients with a history of atrial fibrillation were randomized to receive either dronedarone or placebo, and were followed for 1 year. Dronedarone was found to reduce the recurrence rate of atrial fibrillation at a statistically significant level. However, the magnitude of the reduction in atrial fibrillation was not impressive. Patients treated with placebo had a 77% recurrence rate after one year, while those treated with dronedarone had a 66% recurrence rate. This 11% reduction, while statistically significant, does not make a great difference clinically.
Furthermore, while the dronedarone was well-tolerated, nobody should feel comfortable saying this drug is non-toxic until it is used in longer-term studies. Its cousin, amiodarone, was thought to be remarkably safe for the first 10 years of its use. After more careful observation, amiodarone is now known to have a constellation of unusual and sometimes life-threatening side effects.
The bottom line: Dronedarone may turn out to be reasonably useful as an antiarrhythmic drug - but apparently it's not going to be the "non-toxic amiodarone" we've all been waiting for.