Researchers have found that the gene expression of some CYP450 enzyme isoforms (CYP3A4, CYP1A2, CYP2C9, et al.)and the activity of some CYP450 enzyme isoforms (CYP3A subtypes) decrease in kidney disease (Dong et al., 2020; Ladda and Goralski, 2016), leading to a reduction in drug metabolism and bile excretion in their prototypic or metabolite form. The gene discussed is CYP2C9; the disease is kidney disorder.