Omeprazole, pantoprazole, and CYP2C19 effects on clopidogrel pharmacokinetic-pharmacodynamic relationships in stable coronary artery disease patients.

Purpose: Proton-pump Inhibitors use and CYP2C19 loss-of-function alleles are associated with reduced responsiveness to standard clopidogrel doses and increased cardiovascular events. Methods: Post-myocardial infarction patients heterozygous (wild type [wt]/*2, n = 41) or homozygous (*2/*2, n = 7) for the CYP2C19* 2 genetic variant were matched with patients not carrying the variant (wt/wt, n = 58). All patients were randomized to a 300- or 900-mg clopidogrel loading dose. A PK/PD model was defined using the variation of the P2Y reaction unit relative to baseline. Results: Carriage of CYP2C19* 2 allele and the use of omeprazole/esomeprazole were associated with the inter-individual variability in the active metabolite clearance. The relationship between inhibition of platelet aggregation (IPA, %) and the active metabolite AUC (h*μg/L) was described by a sigmoid function (Emax 56±5%; E 15.9±0.8 h*μg/L) with a gamma exponent (7.04±2.26). Conclusion: This on/off shape explains that a small variation of exposure may have a clinical relevance. [ABSTRACT FROM AUTHOR]