Treatment of rats with INH, RIF, and PZA for 30 days resulted in an increase of the area under the plasma concentration–time curve (AUC0−t) for 6-OH-CZX and a decrease of AUC0−t for CZX compared with the control group, which indicated that the long-term treatment of rats with anti-TB drug can up-regulate the activity of CYP2E1 and accelerate the hydroxylation of CZX to 6-OH-CZX in rats. The gene discussed is CYP2E1; the disease is tuberculosis.