Inhibition of ADP-induced platelet aggregation by clopidogrel is related to CYP2C19 genetic polymorphisms.

1. Clopidogrel is one of the most important antithrombotic drugs but has different efficacies in different populations. The aim of the present study was to evaluate the contribution of CYP2C19 genetic polymorphisms to the inhibition of ADP-induced platelet aggregation by clopidogrel in healthy Chinese volunteers. 2. Eighteen healthy male volunteers (six CYP2C191/CYP2C191, six CYP2C191/CYP2C192and3 and six CYP2C192/CYP2C192and3) were enrolled in the study. Each subject took 300 mg clopidogrel on the first day and then 75 mg once daily for 2 consecutive days. Blood samples were taken to measure ADP-induced platelet aggregation at baseline and 4, 24 and 72 h after administration of the first dose of clopidogrel. 3. There were significant decrease in 2 and 5 micromol/L ADP-induced platelet aggregation at 4, 24 and 72 h after clopidogrel among the three CYP2C19 genotypes compared with baseline (P < 0.001). The change in 5 micromol/L ADP-induced platelet aggregation in subjects with the CYP2C191/CYP2C191 genotype was greater than that in subjects with the CYP2C192/CYP2C192and3 genotype at 4 h (49.0 +/- 15.5 vs 29.7 +/- 17.4%, respectively; P = 0.029), 24 h (48.7 +/- 20.5 vs 25.0 +/- 17.6%, respectively; P = 0.035) and 72 h (45.5 +/- 15.2 vs 26.5 +/- 15.8%, respectively; P = 0.030) after clopidogrel administration. 4. In conclusion, CYP2C192 and CYP2C19*3 genetic polymorphisms reduced clopidogrel inhibition of ADP-induced platelet aggregation, with the degree of inhition dependent on the genetic polymorphism present.