[ tuh-maak-suh-fen ]

Tamoxifen is a medication that is commonly used in the treatment of breast cancer. It belongs to a class of drugs called selective estrogen receptor modulators (SERMs). Tamoxifen works by blocking the effects of estrogen in certain tissues, particularly breast tissue, where estrogen can promote the growth of cancer cells. By inhibiting estrogen's action, tamoxifen helps to slow down or prevent the growth of hormone receptor-positive breast tumors. It is often prescribed for both premenopausal and postmenopausal women diagnosed with estrogen receptor-positive breast cancer. Additionally, tamoxifen has been found to reduce the risk of developing breast cancer in high-risk individuals.

Tamoxifen can have side effects including:

Hot flashes

Increased risk of blood clots


Tamoxifen was developed and researched by a team of scientists at Imperial Chemical Industries (ICI), a British pharmaceutical company. The contributions of researchers such as Arthur Walpole and Dora Richardson were crucial in identifying tamoxifen's potential as an anti-estrogen drug. Through their collective efforts, tamoxifen was discovered, developed, and approved as a treatment for breast cancer.