30ML
Tamoxifen  is an antagonist of the estrogen receptor in breast tissue. It has been the standard endocrine (anti-estrogen) therapy for hormone-positive early breast cancer.  
 
Aromatase inhibitors have been proposed for postmenopausal women. In men, tamoxifen is sometimes used to potentially help treat gynecomastia that arises. For example, as a side effect of antiandrogen prostate cancer treatment.
 
Tamoxifen may potentially competitively bind to estrogen receptors on tumors and other tissue targets.  Producing a nuclear complex that decreases DNA synthesis, and inhibits estrogen effects.
 
It is a nonsteroidal agent with potent antiestrogenic properties, which compete with estrogen for binding sites in breast and other tissues.