Assessment of antithrombotic agents using the platelet aggregation test

Background: A number of antithrombotic agents are available for use in pati ents with arteriosclerotic disease. However, no guidelines have been establ ished for their clinical use. Objective: The purpose of this study was to compare the ability of Various antithrombotic agents to inhibit experimentally induced platelet aggregatio n. Methods: Sixteen angina-free patients who had undergone coronary artery byp ass surgery >6 months before the start of this trial were studied. After a 4-week washout period, ticlopidine hydrochloride (TIG) 400 mg/d, dipyridamo le (DIP) 300 mg/d, cilostazol (CLI;) 200 mg/d, trapidil 300 mg/d, beraprost sodium 120 mug/d, aspirin dialuminate (ASP) 81 mg/d, ethyl icosapentate 18 00 mg/d, and sarpogrelate hydrochloride (SAR) 300 mg/d were administered or ally in sequence for 4 weeks each, and platelet aggregation activity was de termined at the end of each 4-week period. There mere no washout periods be tween medications. Adenosine diphosphate (ADP) 2, 5, and 10 mu mol/L; arach idonic acid 2 mmol/L; and collagen 2 mug/mL were used as agonists. Results: Medication was discontinued in 5 patients-2 patients while receivi ng DIP, 2 while receiving CIL, and 1 while receiving SAR-due to subjective symptoms. TIC suppressed platelet aggregation significantly at all 3 doses of ADP (P < 0.01) and with arachidonic acid (P < 0.01); ASP with ADP 5 and 10 mu mol/L (P < 0.05), arachidonic acid (P < 0.01), and collagen (P < 0.01 ); and CIL with ADP 2 <mu>mol/L (P < 0.01) and atrachidonic acid (P < 0.01) . A marked inhibition of platelet aggregation, as measured by the platelet aggregation test used in this study, was seen with TIC (maximum mean aggreg ation 66.8% reduced to 34.0% with ADP 5 mu mol/L as the agonist), with CIL (72.4% reduced to 29.7% with arachidonic acid as the agonist), and with ASP (72.4% reduced to 3.0% with arachidonic acid as the agonist). Conclusions: These results show that TIC, ASP, and CIL, but not the other 5 agents studied, had a significant antithrombotic effect in this sample of patients, as measured by the platelet aggregation test.