Particularly, for CYP2D4, previous studies that aimed to determine the effects of traumatic brain injury alone and with erythropoietin or anakinra treatment by analyzing gene expression of hepatic inflammatory proteins, drug-metabolizing enzymes, and transporters in a cortical contusion impact injury model showed that traumatic brain injury and erythropoietin treatment decreased the expression of CYP2D4 mRNA, as well as the CYP2D4 protein [50]. Here, EPO is linked to brain injury.