Warfarin is metabolized by the cytochrome P450 (CYP) isozymes in the liver, primarily by the CYP2C9, CYP2C19, CYP2C8, CYP1A2, and CYP3A4.[5] Among the medications that the patient was receiving in the hospital, the suspected drugs are esomeprazole and ceftriaxone, both of them can elevate liver enzymes, and the esomeprazole interacts with warfarin are metabolized by CYP3A4 and CYP2C19.[6] But as the liver injury improved, the warfarin retakes, the liver function was not affected, and this combination was not considered to be the cause of the liver failure. This evidence concerns the gene CYP2C9 and liver failure.