Tamoxifen citrate is a non-steroidal anti-estrogen with a wide use in clinical medicine. It belongs to a class of selective estrogen receptor modulators (SERMs), and also works as an estrogen agonist and antagonist. In some tissues, it can act as estrogen, but in others it blocks the effects of estrogen. In the mammary tissue it acts as a potent anti-estrogen, and consequently is commonly used in the treatment of breast cance