EVALUATION ON EFFECTIVENESS OF LOW DOSE ASPIRIN THERAPY FOR PROTECTION OF THROMBUS FORMATION
In order to protect thrombus formation, administration of low dose aspirin has become common. However, its significance for this purpose is still not clear. Effect of small dose of aspirin (ASA) onplatelet aggregation and ability of malondialdehyde(MDA) formation in platelet by the addition of arachidonic acid in vitro were investigated. In clinical study, platelet aggregation, MDA formation of platelet, serum P-thromboglobulin(p-TG), platelet factor 4(PF4) and thromboxane B2(TX-B2) levelswere measured before and after low doseaspirin therapy.Platelet aggregations by ADP, collagen, epinephrin and arachidonate as inducers were significantly suppressed under 12.5 ug/ml ASA in the medium. MDA formation of platelet was remarkably inhibited under 1.6 ug/ml of ASA in the medium in vitro.In patients, single oral dose of 50 mg ASA showed no change on platelet aggregation while the ability of MDA formation decreased 50# of the before. Serum concentration of ASA after oral dose of 50 mg ASA only showed 1.5 to 6.0 ug/ml at maximum.Daily dose of 50 mg ASA was continued during 10 days. Changes of various factors due to the time course were observed. Inhibitions of platelet aggregation were seen from 5th day on ADP and collagenand from 2nd day on epinephrin and arachidonate as inducers during the therapy. MDA formations of platelet were decreased quickly and it became almost zero at 5th day. ASA levels in the patient serum reached plateau as 8 or 9 ug/ml from 3rdday.Various patients with a possibility of thrombus formation were administered daily 50 mg ASA during 10 days. Platelet aggregations and MDA production, serum β-TG, PF4 and TXB2 levels were measured before and after the therapy. Platelet aggregations by ADP, collagen and epinephrin as inducers were significantly suppressed after the therapyand MDA production of platelet was also markedly decreased after the therapy. There were no significant changes in serumβ-TG and PF4 levels while TXB2 level tended to decrease after the therapy.From these results, it was concluded that daily 50 mg ASA oral dose was certainly effective for protection of thrombus formation.