Abstract: Zhao Yajing, Li Shuixiu, Jiang Ling, Song Yanjun, Guo Hui, Liu Weida, Shen Yongnian, Zhu Kunju, Zhang Hong Institute of Mycology, The First Affiliated Hospital of Jinan University, Guangzhou 510632, China （Zhao YJ, Li SX, Jiang L, Song YJ, Guo H, Zhu KJ, Zhang H）; Department of Mycology, Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing 210042, China （Liu WD, Shen YN） Corresponding authors: Zhu Kunju, Email: zhukunju1111@163.com; Zhang Hong, Email: tzhangh@jnu.edu.cn 【Abstract】 Objective To evaluate the in vitro synergistic effect of tetrandrine on ketoconazole against Candida parapsilosis complex. Methods According to the Clinical and Laboratory Standards Institute （CLSI） M27?A3 guidelines, the microdilution checkerboard method was used to evaluate in vitro antifungal activities of ketoconazole alone and in combination with tetrandrine against 21 clinical isolates of Candida parapsilosis complex based on the fractional inhibitory concentration index （FICI）. Antifungal effects of the above drugs at different time points were evaluated by the XTT assay, and then time?killing curves were drawn and assessed to investigate the in vitro dynamic antifungal activity. Results The minimum inhibitory concentrations （MICs） of tetrandrine and ketoconazole alone against 21 clinical isolates of Candida parapsilosis complex were 32 - 64 mg/L and 0.031 25 - 2 mg/L, respectively. When ketoconazole was combined with tetrandrine, MICs of tetrandrine and ketoconazole were reduced to 2 - 8 mg/L and 0.008 - 0.25 mg/L respectively, and the FICI ranged from 0.09 to 0.5. The time?killing curves revealed that the fungal growth was delayed obviously in the combination group compared with the ketoconazole alone group and tetrandrine alone group. Conclusion Tetrandrine has obvious synergistic effects on ketoconazole against Candida parapsilosis complex in vitro.