According to the company, dronedarone showed a decrease of safety events versus amiodarone but more occurrences of the composite primary endpoint.
There were 184 patients (73.9%) who reached the primary endpoint in the dronedarone arm as compared to 141 (55.3%) in the amiodarone arm (p<0.001). In the primary endpoint, atrial fibrillation after electrical cardioversion occurred in 36.5% of patients in the dronedarone arm versus 24.3% of patients in the amiodarone arm. Patients on amiodarone tended to experience more premature drug discontinuation (34 versus 26) than patients on dronedarone.
The Dionysos trial also showed a decrease of 20% favoring dronedarone versus amiodarone (83 versus 107, p=0.1291) in the predefined main safety endpoint. The predefined main safety endpoint included thyroid, hepatic, pulmonary, neurological, skin, ocular, and gastrointestinal adverse events as well as premature study drug discontinuation due to any adverse event.
When excluding gastrointestinal side effects from the main safety endpoint, as also predefined in the protocol, there was a statistically significant decrease of 39% favoring dronedarone (61 versus 99/p=0.0021), the company said.
John Camm, professor at St George’s University of London, said: These results are as expected. Amiodarone – more effective on ECG atrial fibrillation recurrence but at high cost of organ toxicity over the long term – should remain the antiarrhythmic treatment of last resort in all patients other than those with severe heart failure.