Tamoxifen (Oral)

Tamoxifen (By Mouth)

Tamoxifen (ta-MOX-i-fen)

Treats advanced breast cancer in men and women, and early breast cancer in women. Also may prevent breast cancer in women who are at a high risk because of age, family history, or other factors.

Brand Name(s):

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

You should not receive this medicine if you have had an allergic reaction to tamoxifen, if you are also taking blood thinners such as Coumadinreg;, or if you have ever had blood clotting problems. Do not use this medicine if you are pregnant.

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.  
  • Your doctor will tell you how much of this medicine to use and how often. Do not take more medicine or take it more often than your doctor tells you to. 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.

If a dose is missed::

  • If you miss a dose or forget to take your medicine, take it as soon as you can. If it is almost time for your next dose, wait until then to take the medicine and skip the missed dose. Do not use extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine:

  • Store the medicine at room temperature, away from heat, moisture, and direct light. Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.  
  • Keep all medicine away from children and 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 (Cytadrenreg;), bromocriptine (Parlodelreg;), letrozole (Femarareg;) 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, such as condoms.

Warnings While Using This Medicine:

  • Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant during the time you are using this medicine and for at least 2 months after you stop treatment. If you think you have become pregnant, tell your doctor right away.  
  • Make sure your doctor knows if you are breastfeeding, or if you have High cholesterol, high triglycerides, or cataracts. 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 lung, or cancer of the uterus. Discuss these risks and your personal situation with your doctor.  
  • 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.  
  • It is important to have regular gynecologic check-ups while you are taking tamoxifen.  
  • Some of the side effects of this medicine may not appear for months or years, or after you have stopped using this medicine.

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 face or hands, swelling or tingling in the mouth or throat, tightness in chest, trouble breathing  
  • Blurred vision, increased sensitivity of eyes to bright light, change in color vision  
  • Excessive nausea, vomiting, thirst  
  • Heavy or abnormal vaginal bleeding, pelvic pain or pressure  
  • New breast lumps  
  • Shortness of breath, coughing up blood, pain or numbness in your leg, chest, or calf  
  • Sudden, severe headache, slurred speech, sudden loss of coordination  
  • Unusual bleeding, bruising, or weakness  
  • Yellow eyes or skin, dark-colored urine or pale stools, nausea, vomiting, loss of appetite, pain in the upper stomach

If you notice these less serious side effects, talk with your doctor:

  • Hot flashes  
  • Loss of interest in sex or trouble having sex (in men)

Johns Hopkins patient information

Copyright 1996-2014 Cerner Multum, Inc. Version: 16.02.
Revision date: July 9, 2011
Last revised: by Sebastian Scheller, MD, ScD

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The drug reference included in this section is provided by Cerner Multum, Inc., of Denver, Colorado. Armenian Medical Network receives monthly updates from Multum.