The reasons of clopidogrel (CLP) resistance are still unclear. The response to CLP may be influenced by both genetic and non‐genetic factors. Among genetic factors, common polymorphisms in the gene coding glycoprotein‐P (P‐gp, MDR1 and ABCB1) are considered as potential determinants of the efficacy of CLP treatment. The aim of this study was to evaluate the influence of ABCB1 3435C>T genetic polymorphism on the pharmacokinetics and pharmacodynamics of CLP and its metabolites: diastereoisomers of thiol metabolite (the inactive H3 and the active H4) and inactive carboxylic derivative.

The study group included 42 patients undergoing elective coronary angiography and percutaneous coronary intervention. The plasma concentrations of CLP and its metabolites were measured by a validated HPLC‐MS/MS method. Whole‐blood aggregation was determined with Multiplate analyzer. For evaluation of ABCB1 3435C>T polymorphism, PCR‐RFLP method was applied.

It was found that Exposition to the unchanged CLP, measured by AUC_0–t of the drug, was significantly lower (P = 0·012) in TT homozygotes comparing to that observed in CC and CT genotypes, although no correlation was found between platelet aggregation and ABCB1 genetic polymorphism.

Our findings show that the presence of 3435C>T allele has an impact on CLP pharmacokinetics but not on the drug pharmacodynamics. Therefore, the 3435C>T genotype may not be the primary determinant influencing the pharmacokinetics of the active H4 metabolite and antiplatelet effect of the drug.