To choose a suitable dose of aspirin (ASA) in ASA therapy, two small doses of ASA were administered to healthy volunteers and to patients with thromboembolism. From examination of platelet aggregation and malondialdehyde (MDA) formation after administration of ASA for a week, it was found that the pharmacologically effective dose of ASA as an anti-platelet drug was less than 50mg, since about 90% of MDA formation was inhibited after administration of 50mg of ASA. Furthermore, it was also observed that the average inhibition in all subjects examined was 70% after administration of 10mg of ASA. However, as the effects of 10mg of ASA on platelet aggregation and MDA formation were different from case to case, it seems reasonable that a suitable dose of less than 50mg of ASA should be selective by measuring platelet aggregation and MDA formation of each patient after ASA therapy. Although changes in platelet aggregation and MDA formation after ASA therapy were different between healthy male and healthy female volunteers, there was no marked difference between male patients and female patients.
