Association of the use of amlodipine with clopidogrel response in Chinese patients undergoing percutaneous coronary intervention

Until recently, the precise mechanism of clopidogrel resistance remains unclear. Some clinical studies have demonstrated that calcium channel blockers (CCBs) could reduce the antiplatelet effect of clopidogrel in white or black subjects, implicating in clopidogrel resistance. However, that remains to be determined in Chinese patients. In this study, we sought to determine whether there could be a decreased antiplatelet effect of clopidogrel and an increased risk for developing adverse cardiovascular events after concomitant use of different CCBs and clopidogrel in Chinese patients treated with percutaneous coronary intervention (PCI). A subcohort of 249 patients not carrying the CYP2C19 *2, *3 or *17 variant was identified from a total of 617 consecutive clopidogrel-treated patients undergoing PCI and then categorized into three groups according to various CCB treatments. Baseline data, clinical characteristics and blood samples were collected for all patients. The maximum platelet aggregation (MPA) was measured by light transmittance aggregometry (LTA) to assess the platelet function in blood samples obtained from patients on day 3 after starting daily clopidogrel maintenance doses. The primary clinical end-point was a definite stent thrombosis (ST) episode, whereas secondary end-points were other major adverse cardiovascular events within 12 months after stenting. Of the 249 patients not carrying CYP2C19 *2, *3 and *17 variants, the ADP-induced MPA differed significantly among the three groups (P < 0.001). The MPA values were 1.76 times in the amlodipine group (41.6 ± 23.0%) than in the No CCB group (23.7 ± 14.1%) (P < 0.001). Moreover, in a linear regression model, the use of amlodipine was independently associated with MPA values (R = 0.375,P < 0.001), suggesting that the use of amlodipine might link to the increased MPA. However, the incidence of 1-year ST was not significantly higher in the amlodipine group than the No CCB group (OR, 4.80; 95% CI, 0.87 to 26.52; P = 0.068), and none of the risks for other adverse cardiovascular events were significantly different across the three groups (P = 0.11).