Abstract
The second European Stroke Prevention Study (ESPS-2) reported additivistic effects of dipyridamole (DP) when combined with aspirin (ASA) in the secondary prevention of ischemic stroke. We therefore investigated the inhibitory effects of DP and ASA on platelet aggregation and ATP release from platelets in whole blood from 10 healthy male volunteers in vitro. ADP-induced platelet aggregation in the whole blood was inhibited by 20 μM DP but not by 20 pM ASA. ADP-or collagen-induced ATP release from platelets in the whole blood was inhibited by 20 ltM ASA but not by 20 μM DP. These findings suggest that a combination of DP and ASA is more effective than either alone for the secondary prevention of stroke by simultaneously inhibiting platelet aggregation and dense granule release from platelets in vitro. We also examined the effects of DP and ASA on the plasma levels of adenosine. DP, but not ASA, displayed a tendency towards increasing the plasma levels of adenosine. This effect might be related to inhibition of platelet aggregation by DP.
