Abstract:【Objective】 To investigate the effects of Cryptotanshinone on CYP3A4 and CYP2C9 expressions in Chang liver cells, confirm its effect on cytochrome P450 enzyme and analyze the drug-drug interaction so as to lay a foundation for rational medicine administration. 【Methods】 CCK-8 assay was performed to determine the proliferation of Chang liver cells after treatment with Cryptotanshinone for 1 day, 3 and 7 days. Quantificational reverse transcription polymerase chain reaction and Western blot were performed to determine mRNA and protein expressions of CYP3A4 and CYP2C9 respectively. 【Results】 After 1-day treatment, Cryptotanshinone had no effect on protein or mRNA expression of CYP3A4. However, Cryptotanshinone significantly inhibited the mRNA and protein expressions of CYP3A4 (P < 0.05) after 3- and 7-day treatment, and had no significant effect on the mRNA and protein expressions of CYP2C9 after 1-, 3- or 7-day treatment. 【Conclusions】 Continual administration of Cryptotanshinone could inhibit the protein and mRNA expressions of CYP3A4, which suggests that the drug-drug interaction should be concerned about in clinic.