Tamoxifen

Medical use

Breast cancer

Tamoxifen is currently used for the treatment of both early and advanced estrogen receptor-positive (ER-positive or ER+) breast cancer in pre- and post-menopausal women. Additionally, it is the most common hormone treatment for male breast cancer. It is also approved by the FDA for the prevention of breast cancer in women at high risk of developing the disease. It has been further approved for the reduction of contralateral (in the opposite breast) cancer. The use of tamoxifen is recommended for 10 years.

In 2006, the large STAR clinical study concluded that raloxifene is equally effective in reducing the incidence of breast cancer, but after an average 4-year follow-up, although the difference was not statistically significant, there were 36% fewer uterine cancers and 29% fewer blood clots in women taking raloxifene than in women taking tamoxifen.

Infertility

Tamoxifen is used to treat infertility in women with anovulatory disorders. It is given at days 3 to 7 of a woman's cycle.

Tamoxifen improves fertility in males with infertility by disinhibiting the hypothalamic–pituitary–gonadal axis (HPG axis) via ER antagonism and thereby increasing the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) and increasing testicular testosterone production.

Gynecomastia

Tamoxifen is used to prevent or treat gynecomastia. It is taken as a preventative measure in small doses, or used at the onset of any symptoms such as nipple soreness or sensitivity. Other drugs are taken for similar purposes such as clomifene and the anti-aromatase drugs which are used in order to try to avoid the hormone-related adverse effects.

Others

Occasionally tamoxifen is used in treatment of the rare conditions of retroperitoneal fibrosis and idiopathic sclerosing mesenteritis.