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Trade/other name(s): Nolvadex, Soltamox

Why would this drug be used?

Tamoxifen is used to prevent breast cancer in high-risk women; decrease the risk of getting invasive breast cancer in women with ductal cancer in situ (DCIS); help keep cancer from coming back after surgery, radiation, and chemotherapy; and to treat advanced breast cancer. It is also used to treat other types of cancer, and may be used for other conditions.

How does this drug work?

Tamoxifen is a special type of hormone drug called a selective estrogen-receptor modifier or SERM. This drug binds to estrogen receptors. In the cells of some tissues (like the breast), this blocks the action of estrogen, so that cells (like some cancer cells) that need estrogen to divide stop growing and die. In other cells and tissues (like the bones and the uterus), tamoxifen acts like a weak estrogen

Before taking this medicine

Tell your doctor…

  • If you are allergic to anything, including medicines, dyes, additives, or foods.
  • If you have any medical conditions such as kidney disease, liver disease (including hepatitis), heart disease, congestive heart failure, diabetes, gout, or infections. These conditions may require that your medicine dose, regimen, or timing be changed.
  • If you have ever had blood clots or a stroke. You may not be able to take tamoxifen, since it can increase the risk of blood clots in the leg or arm, the lungs, or brain (stroke).
  • If you have cataracts. Tamoxifen can make them worse, and your doctor may want to watch you for this.
  • If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. This drug may cause harm to the fetus if the woman is taking it at the time of conception or during pregnancy. Check with your doctor about what kinds of birth control can be used with this medicine.
  • If you are breast-feeding. It is not known whether this drug passes into breast milk. If it does, it could harm the baby.
  • About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

Tamoxifen should not be used with estrogens including most types of birth control pills (oral contraceptives) because they may interfere with tamoxifen's effects.

Medicines that keep blood from clotting, such as warfarin (Coumadin) can have increased effects while taking tamoxifen, and dose may need to be adjusted to avoid bleeding.

Certain drugs may make tamoxifen less effective:

  • Antidepressants such as fluoxetine (Prozac, Serafem), paroxetine (Paxil), bupropion (Wellbutrin, Zyban), duloxetine (Cymbalta), and sertraline (Zoloft)
  • Quinidine (Cardioquin) or amiodarone (Cordarone), drugs for heart rhythm
  • Diphenhydramine (Benadryl), antihistamine
  • Thioridazine (Mellaril), antipsychotic
  • Cimetidine (Tagamet), stomach acid blocker

Certain chemotherapy medicines (cytotoxic drugs) may further increase the risk of blood clots while on tamoxifen.

The TB drug rifampin, and the anti-seizure drugs phenobarbital and phenytoin may also affect tamoxifen.

If tamoxifen is given with anastrozole or letrozole, tamoxifen lowers the levels of these drugs in the blood.

Check with your doctor, nurse, or pharmacist about other medicines, vitamins, herbs, and supplements, and whether alcohol can cause problems with this medicine.

Interactions with foods

No serious interactions with food are known at this time. Check with your doctor, nurse, or pharmacist about whether foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Tamoxifen is taken by mouth once or twice a day with an 8 oz glass of water, with or without food. The dose depends on why you are taking it. Take this drug exactly as told to by your doctor. If you do not understand the instructions, ask your doctor or nurse to explain them to you.

Keep the medicine in a tightly closed container away from heat and moisture and away from children and pets.


When you start taking tamoxifen for cancer treatment, you may get a "flare" reaction -- worsened symptoms that usually improve on their own. You may have increased bone pain and/or tumor pain. Talk to your doctor or nurse if you need extra pain medicines during this time. Tell your doctor if this does not go away within 2 weeks.

Women who have not been through menopause may take this drug. Even though it does not cause menopause, it can cause menopause-like symptoms, such as hot flashes, vaginal dryness, thinning hair, and irregular bleeding. Talk with your doctor if this is a problem for you.

It is important to keep taking tamoxifen, even if you feel well. If you are bothered by side effects, talk to your doctor or nurse to find out if the problems are serious. Many side effects can be managed with help from your doctor.

Tamoxifen can cause high calcium levels in the blood the first couple of weeks if it is taken by women with breast cancer that has spread to bones. This is a rare but serious problem. Call your doctor if you notice symptoms such as feeling tired, trouble thinking clearly, lack of appetite, pain, increased thirst and urination, constipation, or nausea and vomiting.

Very rarely, this drug can cause blood clots. Sometimes they form in the arm or leg. Clots may cause heart attack, stroke, or blockage in the lungs. Call your doctor or nurse right away if you develop pain in your lower leg (calf), redness or swelling of your arm or leg, shortness of breath, chest pain, coughing up blood, sudden severe headache, confusion, dizziness, numbness, or trouble speaking or moving.

Before you have any type of surgery, be sure the doctor knows that you are taking this drug.

Carefully avoid pregnancy while taking tamoxifen and for at least 2 months after it is stopped. Talk with your doctor about what method is best for you. Tamoxifen can harm an unborn baby.

Depending on a woman's menopausal status, tamoxifen can have different effects on the bones. Taken before menopause tamoxifen can cause some bone thinning, but after menopause it is often good for bone strength.

Because of the way this drug acts on the body, there is a chance that it can cause other effects that may happen months or years after the drug is used. Such side effects rarely can include a second cancer, such as endometrial (uterine) cancer. Because of this, it is important to call your doctor if you notice new breast lumps, irregular menstrual periods, changes in vaginal discharge, pelvic pain, or pressure in the pelvic area, even if it has been years since your treatment. If you are getting this drug, your doctor feels this risk is outweighed by the risk of what might happen if you do not get this drug. You may want to discuss these risks with your doctor.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.


  • Tiredness (usually goes away after taking the drug a few weeks)
  • Hot flashes*

Less common

  • Irregular menstrual bleeding*
  • Vaginal discharge or bleeding
  • Changes in mood
  • Milk production in the breast
  • "Flare" reaction (symptoms briefly worsen) when starting the drug*
  • Weight gain
  • Bone thinning (if taken before menopause)*


  • Nausea
  • Vomiting
  • Cataracts and other changes in eyesight
  • Rash
  • Swelling/pain in hands or feet
  • Headache
  • Dizziness
  • Hair thinning*
  • Decreased sexual desire and sometimes impotence in men
  • Vaginal dryness*
  • Low white blood cell count with increased risk of infection
  • Low platelet count with increased risk of bleeding
  • Increase in calcium blood level in the first 2 weeks of treatment*
  • Blood clots with symptoms such as pain in leg or calf, sudden shortness of breath, pain in the chest, trouble moving or speaking (stroke)*
  • Allergic reaction with itching, rash, hives, swelling in mouth or throat, trouble breathing
  • Fetal harm if pregnancy occurs during or 2 months after stopping the drug*
  • Increased risk of cancer of the uterus*

*See the "Precautions" section for more detailed information.

There are other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved before 1984. (FDA cannot verify dates of drugs approved before 1984.)

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 01/19/2012
Last Revised: 12/27/2012