Tamoxifen (By mouth)
Antiestrogen (About this – PubMed Health)
Uses of This Medicine
Tamoxifen is a medicine that blocks the effects of the estrogen hormone in the body. It is used to treat breast cancer in women or men. It may also be used to treat other kinds of cancer, as determined by your doctor.
Tamoxifen also may be used to reduce the risk of developing breast cancer in women who have a high risk of developing breast cancer. Women at high risk for developing breast cancer are at least 35 years of age and have a combination of risk factors that make their chance of developing breast cancer 1.67% or more over the next 5 years. Your doctor will help to determine your risk of developing breast cancer.
The following are risk factors that may increase your chance of developing breast cancer:
If you have close family members (mother, sister, or daughter) with breast cancer.
If you have ever had a breast biopsy or if high-risk changes in your breast(s) have been found from a breast biopsy.
If your first menstrual period occurred at an early age.
The exact way that tamoxifen works against cancer is not known, but it may be related to the way it blocks the effects of estrogen on the body.
Before you begin treatment with tamoxifen, you and your doctor should talk about the good this medicine will do as well as the risks of using it.
Tamoxifen is available only with your doctor’s prescription.
Once a medicine has been approved for marketing for a certain use, experience may show that it is also useful for other medical problems. Although these uses are not included in product labeling, tamoxifen is used in certain patients with the following medical conditions:
Breast cancer, neoadjuvant treatment for hormone receptor-positive disease in postmenopausal women.
Other uses (PubMed Health)
How To Use
Medicines used to treat cancer are very strong and can have many side effects. Before receiving this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.
This medicine should come with a Medication Guide. Ask your pharmacist for a copy if you do not have one.
Your doctor will tell you how much medicine to use. Do not use more than directed. You may need to take this medicine for 5 years or longer.
Swallow the tablet whole. You may take this medicine with or without food.
Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.
Take this medicine at the same time each day.
If a dose is missed:
Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
How to Store and Dispose of This Medicine:
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Do not store in the refrigerator or freezer.
Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any leftover medicine after you have finished your treatment. You will also need to throw away old medicine after the expiration date has passed.
Keep all medicine out of the reach of children. Never share your medicine with anyone.
Drugs and Foods to Avoid
Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.
Birth control pills, implants, or shots may not work while you are using tamoxifen. To keep from getting pregnant, use another form of birth control. Other forms include condoms, a diaphragm, or contraceptive foam or jelly.
When Not To Use
You should not use this medicine if you have had an allergic reaction to tamoxifen, or if you are pregnant. You should not use this medicine if you are also using blood thinners (such as warfarin, Coumadin®), or if you have had a blood clot or blood clotting problems.
It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant. Keep using effective birth control for at least 2 months after you stop treatment.
To make sure you are not pregnant, you may start taking this medicine while you are having your menstrual period. Also, you must have a negative pregnancy test before you will be allowed to take this medicine.
Do not breastfeed while you are using this medicine.
Your doctor will check your progress and the effects of this medicine at regular visits. Keep all appointments. It is important for women to have regular gynecologic check-ups while taking tamoxifen.
Make sure any doctor or dentist who treats you knows that you are using this medicine.
This medicine may increase your risk of developing other rare but serious conditions, such as stroke, a blood clot in the lungs or veins, or cancer of the uterus. Talk with your doctor about these risks and your personal situation.
Some of the side effects of this medicine may not appear for months or years, or after you have stopped using this medicine. Tell your doctor if you have later side effects.
Liver problems may occur while you are using this medicine. Stop using this medicine and check with your doctor right away if you are having more than one of these symptoms: abdominal pain or tenderness; clay-colored stools; dark urine; decreased appetite; fever; headache; itching; loss of appetite; nausea and vomiting; skin rash; swelling of the feet or lower legs; unusual tiredness or weakness; or yellow eyes or skin.
Possible side effects
Summary More details
Call your doctor right away if you notice any of these side effects:
Chest pain, shortness of breath, or coughing up blood.
Dark-colored urine or pale stools.
Heavy or abnormal vaginal bleeding, pelvic pain or pressure.
Nausea, vomiting, loss of appetite, or pain in your upper stomach.
New breast lumps.
Numbness or weakness in your arm or leg, or on one side of your body.
Pain in your lower leg (calf).
Sudden or severe headache, or problems with vision, speech, or walking.
Swelling in your hands, ankles, or feet.
Unusual bleeding, bruising, or weakness.
Yellowing of your skin or the whites of your eyes.
If you notice these less serious side effects, talk with your doctor:
Back or joint pain.
Blurred vision, change in color vision.
Hot flashes, vaginal discharge.
Loss of interest in sex or trouble having sex (in men).
Trouble with sleeping.
If you notice other side effects that you think are caused by this medicine, tell your doctor.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
More side effects of this drug
Brand names include
There may be other brand names for this medicine.