Fig. 6

Diagram of the drug-drug interaction between BZ formula and tamoxifen in breast cancer and depression. Tamoxifen is primarily metabolized to N-desmethyltamoxifen in a process mediated by CYP3A4 [3], followed by CYP2D6-mediated oxidation to 4-hydroxy-N-desmethyltamoxifen (endoxifen) [4]. Mangiferin but not timosaponin BII, derived from BZ formula, inhibited P450 activity in rat liver microsomes. BZ formula attenuated the efficacy of tamoxifen against breast cancer. However, tamoxifen did not affect the antidepressant activity of BZ formula or timosaponins, but did inhibit mangiferin. In summary, BZ formula attenuated the efficacy of tamoxifen against breast cancer through CYP450 enzyme activity