TAMOXIFEN CITRATE is a nonsteroidal agent that has demonstrated potent antiestrogenic effects related to its ability to compete with estrogen for binding sites in target tissues. Tamoxifen citrate is an oral anti-estrogen and estrogen antagonist which competes with estrogen at the receptor sites reducing estrogenic expression. Tamoxifen citrate is a Selective Estrogen Receptor Modular (SERM) acting via estrogen site competition as opposed to Aromatase Inhibitor (AI) drugs which prevent aromatase derived estrogens from being created.