There is evidence that drugs such as warfarin (CYP2C9 substrate) and midazolam (CYP3A4 substrate) have altered pharmacokinetics in CKD, although the mechanism for these observations is controversial (Dreisbach et al, 2003; Nolin et al, 2009; Thomson et al, 2015; Tuey et al, 2022). This evidence concerns the gene CYP2C9 and chronic kidney disease.