Tamoxifen blocks the actions of estrogen, a female hormone. Certain types of breast cancer require estrogen to grow.
Tamoxifen is used to treat some types of breast cancer in men and women. It is also used to lower a woman's chance of developing breast cancer if she has a high risk (such as a family history of breast cancer).
Tamoxifen may also be used for purposes not listed in this medication guide.
Do not use tamoxifen if you are pregnant. It could harm the unborn baby. Use a barrier form of birth control (such as a condom or diaphragm with spermicide) while you are using this medication and for at least 2 months after your treatment ends. You should not use tamoxifen if you are allergic to it, or if you have a history of blood clots in your veins or your lungs, or if you are also taking a blood thinner such as warfarin (Coumadin).
Before using this medicine, tell your doctor if you have liver disease, high triglycerides (a type of fat in the blood), a history of cataract, or a history of stroke or blood clot. Also tell your doctor if you if you are receiving chemotherapy or radiation treatment.