Tamoxifen is a drug taken orally in pill form.
For nearly twenty years, physicians have prescribed tamoxifen to help treat patients with advanced breast cancer. Tamoxifen has been shown to help prevent the original breast cancer from returning after breast surgery while also hindering the development of new cancers in the opposite breast. To grow and reproduce, breast cancer cells require the female hormone estrogen. By blocking estrogen in the breast, tamoxifen helps slow the growth and reproduction of breast cancer cells. While tamoxifen fights estrogen in breast cancer cells, it also mimics the positive effects of estrogen in other body systems.