In vitro metabolic interactions between black cohosh (Cimicifuga racemosa) and Tamoxifen

摘要

Women with a history of ER-positive breast cancer taking tamoxifen (TAM) as a chemoprevention agent often suffer from hot flashes as a side effect. To manage these hot flashes, many women taking TAM also use the botanical dietary supplement black cohosh (Cimicifuga racemosa L.). TAM undergoes extensive oxidation by cytochrome P450 2D6 and 3A4 to the active metabolites 4-hydroxy-TAM and 4-hydroxy-N-demethyl TAM (endoxifen). In addition, CYP3A4 converts TAM into alpha-hydroxy-TAM which has been implicated in toxicity of TAM. The purpose of the present study was to examine whether black cohosh might interfere with the efficacy of TAM by inhibiting the production of active metabolites.