Dronedarone exerts anticoagulant and antiplatelet effects independently of its antiarrhythmic actions.

BACKGROUND AND AIMS: Dronedarone reduced the rate of stroke and transient ischemic attack in patients with paroxysmal atrial fibrillation (AF) in the ATHENA trial. This cannot be explained by its antiarrhythmic effect alone and may involve alternative mechanisms. This study aimed to investigate any direct effect of dronedarone on blood thrombogenicity, independent of its antiarrhythmic effects.

METHODS

Blood samples from patients with cardiovascular disease (n = 30) taking no anticoagulant or antiplatelet medication except aspirin were incubated with dronedarone's active metabolite (SR35021A) at 66 ng/ml (am-L) and 119 ng/ml (am-H), i.e., minimum and maximum mean Cmax reported after repeated 400 mg BID dosing. A third aliquot of blood was incubated with vehicle (Control). Antithrombotic effects of dronedarone were assessed using Coagulation Time (CT), Clot Formation Rate (CFR) and Maximum Clot Firmness (MCF) in ThromboElastoMetry and whole blood platelet aggregation in response to ADP, collagen and TRAP.

RESULTS

Compared to Control, mean CT was prolonged by am-L and am-H (164 ± 25 s vs. 180 ± 22 and 182 ± 32 s, respectively, p<0.01 for both). Small but statistically significant reductions were observed in CFR (am-L and am-H) and MCF (am-H). Platelet aggregation induced by ADP and TRAP was also reduced (p<0.05 for both) by am-H.

CONCLUSIONS

Dronedarone exerts direct anticoagulant and antiplatelet effects on human blood in vitro that are independent of its antiarrhythmic actions. This suggests the reductions in ischemic events reported with dronedarone may not be due to amelioration of AF itself. Additional clinical studies are required to further improve understanding of the mechanisms involved.