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Purpose: This study aimed to investigate the pharmacodynamic effects of indobufen and low-dose aspirin in patients with coronary atherosclerosis. Methods: In the first phase, 218 patients with coronary atherosclerosis were randomly assigned to receive aspirin 100 mg once daily (standard dose); 100 mg once every 2 days; 100 mg once every 3 days; 50 mg twice daily; 75 mg once daily; 50 mg once daily; or indobufen 100 mg twice daily for 1 month. In the second phase, 20 healthy subjects were treated with indobufen 100 mg twice daily for 1 week followed after a 2-week washout by aspirin 100 mg once daily for 1 week. The primary outcome was arachidonic acid-induced platelet aggregation (PLAA), and the secondary outcomes included plasma thromboxane B2 (TXB2) and urinary 11-dehydro-TXB2 (11-dh-TXB2) levels at the end of each treatment. Results: In the first phase, compared with aspirin 100 mg once daily: all aspirin groups had similar suppression of PLAA whereas indobufen group had significantly less suppressed PLAA. Aspirin given every second or third day, and indobufen produced less suppression of plasma TXB2. All treatment regimens produced similar inhibition of 11-dh-TXB2. In the second phase, compared with aspirin, indobufen produced less suppression of plasma TXB2 at 8 h and 12 h after the last dose. Conclusions: Aspirin 50 mg twice daily, 75 mg once daily, and aspirin 50 mg once daily produce antiplatelet effects that are similar to aspirin 100 mg once daily. Aspirin given less often than once daily and indobufen 100 mg twice daily do not suppress platelets as effectively as aspirin 100 mg once daily. [ABSTRACT FROM AUTHOR]

Objective: This study was aimed to determine how platelet reactivity (PR) on dual antiplatelet therapy predicts ischemic and bleeding events in patients underwent percutaneous coronary intervention (PCI). Design: A total of 2768 patients who had received coronary stent implantation and had taken aspirin 100 mg in combination with clopidogrel 75 mg daily for > 5 days were consecutively screened and 1885 were enrolled. The recruited patients were followed-up for 12 months. The primary end-point was the net adverse clinical events (NACE) of cardiovascular death, nonfatal myocardial infarction (MI), target vessel revascularization (TVR), stent thrombosis (ST) and any bleeding. Result: 1709 patients completed the clinical follow-up. By using the receiver operating characteristic (ROC) curve analysis, the optimal cut-off values were found to be 37.5 and 25.5% respectively in predicting ischemic and bleeding events. Patients were classified into 2 groups according to PR: inside the window group (IW) [adenosine diphosphate (ADP) induced platelet aggregation (PLADP) 25.5–37.4%)] and outside the window group (OW) (PLADP < 25.5% or ≥ 37.5%). The incidence of NACE was 16.8 and 23.1% respectively in the IW and OW group. The hazard ratio of NACE in IW group was significantly lower [0.69 (95% CI, 0.54–0.89, P = 0.004)] than that in the OW group during 12-month follow-up. Conclusion: An optimal therapeutic window of 25.5–37.4% for PLADP predicts the lowest risk of NACE, which could be referred for tailored antiplatelet treatment while using LTA assay. Trial registration: Trial registration number: ClinicalTrials.govNCT01968499. Registered 18 October 2013 - Retrospectively registered. [ABSTRACT FROM AUTHOR]