Genomic DNA was extracted from peripheral blood leukocytes. The genotypes of the CYP2C19*2 (c.681G>A, rs4244285), *3 (c.636G>A, rs4986893), and *17 (c.-806C > T, rs12248560) variants were determined by the TaqMan genotype discrimination method (Applied Biosystems, Foster City, CA, USA) using commercially available primers and probes purchased from the Assay-on-Demand system.