Objective: The goal of the present study is to explore the interactions between Wutou Tang and CYP3A4 enzyme by determining the influence of Wutou tang on the activity of CPY3A4 in rat liver microsomes. Method: Fifty male SD rats were randomly divided into five groups. 3 groups were intragastrically treated with Wutou tang high dose (2 times of the original prescription dose)

medium dose (original prescription dose) and low dose (0.5 times of the original prescription dose) for 7 consecutive days

respectively. Drinking water was given intragastrically to blank control group and SKF-525A (0.1 g·kg-1) was given intragastrically to inhibitory control group. The activity of CPY3A4 was determined by UPLC method using testosterone as probe in vitro. Result: Compared with the blank control group

the testosterone metabolic rates were significantly lower of groups which were treated with Wutou tang high dose

medium dose and low dose (P<0.05). The testosterone metabolic rates of Wutou tang high dose group was lower than Wutou tang medium dose group and low dose group. Conclusion: The activity of CPY3A4 was significantly inhibited with the continuous use of Wutou tang

which indicates that taking Wutou tang with CYP3A4 enzyme substrates might cause drug interactions.