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SummaryClopidogrel is a prodrug that has to be converted in vivo to its active metabolite by cytochrome (CYP)P450 iso-enzymes. As calcium channel blockers (CCBs) are inhibitors of CYP3A4, concomitant use of these drugs might play a role in the wide inter-individual variability in the response to clopidogrel. However, some CCBs also have strong inhibitory effects on the drug transporter P-glycoprotein (Pgp), which mediates clopidogrel‘s intestinal absorption. It was the aim of this study to evaluate the effect of co-administration of Pgp-inhibiting and non-Pgp-inhibiting CCBs on on-clopidogrel platelet reactivity in patients on dual antiplatelet therapy undergoing elective percutaneous coronary intervention (PCI). In a total of 623 consecutive patients undergoing elective PCI treated with clopidogrel and aspirin, platelet reactivity to 5 and 20 μM adenosine diphospate (ADP) and clopidogrel poor-response (defined as > 70% platelet aggregation to 20 μM ADP) were evaluated by light transmittance aggregometry. A total of 222 patients (35.6%) were on CCB treatment, of which 98 used Pgp-inhibiting CCBs (verapamil, nifedipine, diltiazem, barnidipine) and 124 patients used the non-Pgp-inhibiting CCB amlodipine. Adjusted mean ADP-induced on-clopidogrel platelet reactivity was significantly higher in both users of Pgp-inhibiting CCBs and amlodipine as compared to CCB non-users (all p

The prodrug, clopidogrel, plays an important role in the prevention of thrombotic events in patients undergoing coronary stenting. However, a substantial number of atherothrombotic events still occur, which can partially be explained by heightened residual platelet reactivity. Several studies report that the genetic variation in CYP2C19 (*2) is associated with an impaired response to clopidogrel.To evaluate the effect of genetic variants affecting clopidogrel's absorption (ABCB1 C1236T, G2677T/A, C3435T), metabolism (CYP2C9*2, *3, CYP2C19*3, CYP3A4*1B, and CYP3A5*3), and pharmacodynamics (P2Y1 A1622G) on top of the influence of CYP2C19*2 on platelet reactivity in patients undergoing elective coronary stenting on dual antiplatelet therapy.Platelet function was assessed by light transmittance aggregometry and VerifyNow P2Y12 assay in 428 consecutive patients. Patients were either on chronic clopidogrel maintenance therapy (75 mg/day foror =5 days before the intervention) or received a 300 mg clopidogrel loading dose (1-5 days before the intervention, followed by 75 mg/day). Linear and logistic regressions were used to assess the associations between genetic variants and platelet reactivity and poor responder status.In both the treatment groups, CYP2C19*2-carriage was associated with higher platelet reactivity (P0.002) and poor responder status; 75 mg group: adjusted odds ratio (ORadj): 3.8, 95% confidence interval (CI): 2.0-7.2, 300 mg group: ORadj: 4.1, 95% CI: 1.6-10.4. In the 300 mg group, CYP2C9*3-carriage was associated with higher platelet reactivity (P0.05) and poor responder status (ORadj: 11.1, 95% CI: 1.6-78.8, P=0.016).Besides CYP2C19*2, the variant allele CYP2C9*3 plays an important role in the response to clopidogrel in patients on dual antiplatelet therapy undergoing coronary stenting.

Aims Despite treatment with clopidogrel on top of aspirin, stent thrombosis (ST) still occurs being the most serious complication after percutaneous coronary interventions (PCIs). In this study, we aimed to determine the effect of variations in genes involved in the absorption (ABCB1 C1236T, G2677T/A, C3435T), metabolism (CYP2C19*2 and *3, CYP2C9*2 and *3, CYP3A4*1B and CYP3A5*3), and pharmacodynamics (P2Y1 A1622G) of clopidogrel on the occurrence of ST. Methods and results The selected genetic variants were assessed in 176 subjects who developed ST while on dual antiplatelet therapy with aspirin and clopidogrel and in 420 control subjects who did not develop adverse cardiovascular events, including ST, within 1 year after stenting. The timing of the definite ST was acute in 66, subacute in 87, and late in 23 cases. The presence of the CYP2C19*2 and CYP2C9*3 variant alleles was significantly associated with ST (ORadj: 1.7, 95% CI: 1.0–2.6, P = 0.018 and ORadj: 2.4, 95% CI: 1.0–5.5, P = 0.043, respectively). The influence of CYP2C19*2 (ORadj: 2.5, 95% CI: 1.1–5.5, P = 0.026) and CYP2C9*3 (ORadj: 3.3, 95% CI: 1.1–9.9, P = 0.031) was most strongly associated with subacute ST. No significant associations of the other genetic variations and the occurrence of ST were found. Conclusion Carriage of the loss-of-function alleles CYP2C19*2 and CYP2C9*3 increases the risk on ST after PCI.

Objectives: Formation of collateral circulation is an endogenous response to atherosclerosis, and is a natural escape mechanism by re-routing blood. Inflammatory response- related genes underlie the formation of coronary collaterals. We explored the genetic basis of collateral formation in man postulating interaction networks between functional Single Nucleotide Polymorphisms (SNPs) in these inflammatory gene candidates. Methods: The contribution of 41 genes as well as the interactions among them was examined in a cohort of 226 coronary artery disease patients, genotyped for 54 candidate SNPs. Patients were classified to the extent of collateral circulation. Stepwise logistic regression analysis and a haplotype entropy procedure were applied to search for haplotype interactions among all 54 polymorphisms. Multiple testing was addressed by using the false discovery rate (FDR) method. Results: The population comprised 84 patients with and 142 without visible collaterals. Among the 41 genes, 16 pairs of SNPs were implicated in the development of collaterals with the FDR of 0.19. Nine SNPs were found to potentially have main effects on collateral formation. Two sets of coupling haplotypes that predispose to collateral formation were suggested. Conclusions: These findings suggest that collateral formation may arise from the interactions between several SNPs in inflammatory response related genes, which may represent targets in future studies of collateral formation. This may enhance developing strategies for risk stratification and therapeutic stimulation of arteriogenesis.