Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Blood clots: Tamoxifen may increase the chance of developing blood clots in the lungs or legs. This chance may be further increased if tamoxifen is given with other forms of chemotherapy. If you have a history of blood clots, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
A blood clot in the blood vessels of the brain can prevent blood from reaching parts of the brain, causing a stroke. If you experience signs of a stroke such as confusion, difficulty speaking, loss of coordination, sudden headache or vision changes, contact your doctor as soon as possible.
Cataracts: Tamoxifen may cause cataracts or worsen existing cataracts for some people. If you experience any vision changes while taking this medication, contact your doctor.
High blood calcium levels: Tamoxifen may cause an increase in blood calcium levels for women with breast cancer that has spread to other parts of the body. Your doctor will monitor for this with blood tests.
Uterine cancers: Tamoxifen may increase the chance of developing certain types of uterine cancer. Talk to your doctor about whether any special monitoring is needed. If you experience any vaginal bleeding while or after taking this medication, contact your doctor immediately.
White blood cells and platelets: People with low white blood cells or platelets should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Worsening symptoms: For some women taking this medication, pain may worsen and the size of the affected tissue may increase at the beginning of treatment. This usually resolves within a few weeks of starting tamoxifen. If you experience these effects, contact your doctor.
Pregnancy: This medication may cause birth defects or death to the developing fetus and should not be used during pregnancy. Effective birth control should be used while taking this medication and for about 2 months after finishing it. Tell the doctor immediately if you become pregnant while taking this medication.
Breast-feeding: It is not known if tamoxifen passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.
Children: The safety and effectiveness of using this medication have not been established for children.