Tamoxifen (By mouth)
Treats breast cancer. May prevent breast cancer in women who have a high risk.
When This Medicine Should Not Be Used
How to Use This Medicine
- 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.
- Make sure your doctor knows if you are also using aminoglutethimide (Cytadren®), bromocriptine (Parlodel®), letrozole (Femara®), rifampin (Rifadin®, Rimactane®), or other cancer treatments.
- 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.
Warnings While Using This Medicine
- 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.
- Make sure your doctor knows if you have liver disease, cataracts, eye or vision problems, hypercalcemia (high calcium in the blood), or high cholesterol or triglycerides (fat) in the blood.
- 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.
- This medicine may cause changes in your menstrual periods, which could be a sign of a serious problem. Tell your doctor about any unusual vaginal bleeding or discharge.
- 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 While Using This Medicine
Call your doctor right away if you notice any of these side effects:
- Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
- Chest pain, shortness of breath, or coughing up blood.
- Dark-colored urine or pale stools.
- Fever, chills, cough, sore throat, and body aches.
- 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.
- Constipation, diarrhea, or stomach pain or upset.
- Hot flashes, vaginal discharge.
- Increased tumor pain or bone pain.
- 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
- Last reviewed on 12/4/2015
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