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Trade/other name(s): Fareston

Why would this drug be used?

Toremifene is used to treat advanced breast cancer in postmenopausal women (women who have already gone through menopause and no longer have menstrual periods).

How does this drug work?

Toremifene belongs to the group of drugs called hormones or hormone antagonists. It works by blocking estrogen. The cancer cells that depend on estrogen stop growing and die.

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, high blood pressure, or infections. These conditions may require that your medicine dose, regimen, or timing be changed.
  • If you have had blood clots or a stroke. Rarely, toremifene can cause clots in the leg or arm, the lungs, or brain (stroke).
  • If you have an abnormal heart rhythm, including a disorder of the heart's electrical system called prolonged Q-T interval. You may need closer monitoring during treatment.
  • If you have problems with the amount of magnesium or potassium in your blood. Low levels of these minerals can increase the risk toremifine will affect heart rhythm.
  • If you have any condition that causes the lining of the uterus (womb) to be thicker than usual or grow abnormally. Toremifene may worsen this problem.
  • If you have cataracts in your eyes. Toremifene 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. Although toremifene is normally used for women who have already gone through menopause, this drug may cause harm to the fetus if the woman is taking it at the time of conception or during pregnancy. Women who are taking this drug need to use some kind of birth control if menopause is uncertain. It is important to 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 affect 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

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

A certain kind of blood pressure medicine that causes you to put out more urine (thiazide diuretics) may increase your risk of high calcium levels in the blood (see “Precautions” section).

These drugs can increase your risk of abnormal heart rhythm if you take them during the same times you take toremifene

  • anti-nausea or anti-vomiting drugs such as granisetron (Zofran), dolasetron (Anzemet), or ondansetron (Kytril)
  • anti-psychotic drugs such as thioridazine (Mellaril), haloperidol (Haldol)
  • antidepressants such as venlafaxine (Effexor), amitriptyline (Elavil)
  • heart rhythm drugs such as amiodorone (Cordarone, Pacerone), disopyramide (Norpace), dofetilide (Tikosyn), flecainide (Rhythmol), ibutilide (Corvert), procainamide (Procan, Pronestyl), propafenone (Tambocor), quinidine (Quinidex, Cardioquin), or sotalol (Betapace)

These drugs can raise the levels of toremifene in your blood and cause a higher risk of serious side effects, including heart rhythm problems:

  • antidepressant drugs such as nefazodone (Serzone), fluvoxamine (Luvox), fluoxetine (Prozac, Serafem)
  • antibiotics such as ciprofloxacin (Cipro), levofloxacin (Levaquin), erythromycin (E.E.S., E-Mycin, Erythrocin), or clarithromycin (Biaxin), sparfloxacin (Zagam), or moxifloxacin (Avelox)
  • antifungal drugs such as ketoconazole (Nizoral), itraconazole (Sporanox), voriconazole (Vfend)
  • certain blood pressure medicines such as diltiazem (Cardizem) and verapamil (Calan)
  • HIV drugs such as atazanavir, indinavir, ritonavir, saquinavir, and nelfinavir

Anti-seizure medicines such as phenobarbital (Luminal), clonazepam (Klonopin), carbamazepine (Tegretol), or phenytoin (Dilantin) may cause the body to get rid of toremifene too quickly for it to work as it should.

The TB drugs rifampin, rifampicin, and rifabutin, and the herb St. John's wort, can also make the body get rid of toremifene too quickly.

Other drugs may also interact with toremifene. 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

Some foods, such as grapefruit or grapefruit juice, may raise the level of this drug in your body. This can worsen any bad effects the drug may have on you and may increase its action in a harmful way. Check with your doctor, nurse, or pharmacist about whether other 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?

Toremifene is a pill taken once a day with or without food, and the dose is usually the same for all women. The pill should be taken at the same time every day, if you can. Take this drug exactly as your doctor tells you to. If you do not understand the instructions, your doctor or nurse can explain them to you.

Store the medicine in a tightly closed container away from light, heat, and moisture, and out of the reach of children and pets.


When you start taking toremifene, at first you may get a "flare" reaction -- worsened cancer symptoms that usually get better on their own. Your bone pain and/or tumor pain may get worse, or you may notice that the tumor gets redder or larger. Tell 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.

It is important to keep taking toremifene, even if you feel well. If you have side effects, talk to your doctor or nurse to be sure the problems are not serious, and find out how you can lessen them.

Toremifene can cause high calcium levels in the blood the first couple of weeks 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.

Rarely, this drug can change the heart’s rhythm, especially if taken in high doses, with drugs that raise the blood level of toremifene, or with drugs that can affect heart rhythm. This can cause dizziness, fainting, seizures, and even death. Call your doctor right away if you have any of these symptoms, or you notice a slow or irregular heartbeat.

Very rarely, this drug can cause blood clots. Sometimes they form in the arm or leg. Clots may also cause strokes 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.

Only women who have completed menopause should take this drug. If you suspect that you might still be fertile, talk with your doctor. You should carefully avoid pregnancy while taking toremifene and for a few weeks after it is stopped. Toremifene can harm an unborn baby.

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.


  • hot flashes
  • nausea

Less common

  • irregular menstrual bleeding
  • milk production in breasts
  • vaginal discharge
  • vaginal bleeding
  • "flare" reaction for the first week or two on the drug*


  • loss of appetite
  • tremors
  • skin rash
  • hair loss
  • cataracts or changes in eyesight
  • swelling of hands and feet
  • lower white blood cell count with increased risk of infection
  • lower platelet count with increased risk of bleeding
  • slow or irregular heartbeat (prolonged QT interval)*
  • dizziness, seizures, or fainting due to slow heartbeat*
  • higher 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*
  • fetal harm if pregnancy occurs during or shortly after treatment*
  • death from serious heart rhythm problems*

*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 in 1997.

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: 04/19/2011
Last Revised: 04/19/2011