Patients with underlying liver disease are predisposed to drug-induced liver injury (DILI); patients with NAFLD exhibit an increase in the activity of the CYP2E1, a 1.9–3.1-times diminution in the activity of CYP3A4 in NAFLD, and of NASH, respectively. The gene discussed is CYP3A4; the disease is metabolic dysfunction-associated steatotic liver disease.