tamoxifen

tamoxifen An antiestrogen that competes with estrogen for binding sites in target tissues such as breast tissue and blocks the effects of estrogen there. Tamoxifen may be used to treat breast cancer, help prevent it in women at high risk, and treat women who have had surgery and radiation therapy for ductal carcinoma in situ, to lower the risk of invasive breast cancer arising from the intraductal carcinoma.