Diabetes is a dangerous disease with high risk of vascular complications. Thus, to prevent these vascular complication, antithrombotic drug may be administered. Representative antithrombotic agents are aspirin and cilostazol. However, recent studies suggested that aspirin did not have sufficient effect to prevent vascular complications of diabetes. For that reason, it have been reported that antithrombotic effects of aspirin were falling in diabetes patients, so-called 'aspirin resistance.