Tamoxifen is a drug, which is used to treat and prevent the breast cancer in women and men. It is also used for the treatment of the Albright syndrome. It also helps in improving the fertility in males by disinhibiting the hypothalamic-pituitary-adrenal axis. It may cause serious side-effects including increased risk of stroke, vision problem, pulmonary embolism and uterine cancer.
Tamoxifen serves as a prodrug and have relatively low affinity for its respective target protein, the estrogen receptor (ER). It is metabolized by the cytochrome P450 isoforms in the liver into some active metabolites such as endoxifen and afimoxifene. Endoxifen as well as afimoxifene have around 30-100 times more affinity than tamoxifen with ER.