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Trade/other name(s): Faslodex

Why would this drug be used?

Fulvestrant is used to treat women with advanced breast cancer who have gone through menopause (no longer have menstrual periods). It is generally used when the cancer no longer responds to anti-estrogen medicines like tamoxifen.

How does this drug work?

Fulvestrant is a member of a group of drugs called estrogen receptor down-regulators. Most breast cancer cells have estrogen receptors on their cell surface. Estrogen stimulates these cells with estrogen receptors to divide without regard to the body's estrogen needs. This is referred to as "estrogen-receptor-positive breast cancer." Fulvestrant works by blocking and destroying the estrogen receptor in the cell so that estrogen cannot bind to it. The action effectively lowers (down-regulates) the estrogen receptor activity in the cell so that it acts more like a normal cell.

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 are pregnant, trying to get pregnant, or if there is any chance of pregnancy. There may be an increased risk of harm to the fetus if a woman takes this drug during pregnancy.
  • If you are breast-feeding. It is not known whether this drug passes into breast milk. If it does, it could affect the baby.
  • If you think you might want to have children in the future. This drug has only been tested in women who have gone through menopause, and it may reduce fertility in those who have not. It may also reduce fertility if used in men. Talk with your doctor about the possible risk with this drug and the options that may preserve your ability to have children.
  • 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

No serious interactions are known at this time. But this does not necessarily mean that none exist.

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?

Fulvestrant is typically given by injection into the buttock muscle, once a month. It can be a single shot, or the dose can be divided into 2 shots. The dose is usually the same for all women.


Rarely, fulvestrant can cause high calcium levels in women with breast cancer that has spread to bones. 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.

Fulvestrant should not be taken by pregnant women or those who have not gone through menopause. Call your doctor if you notice vaginal bleeding while taking this medicine.

Avoid pregnancy during and for at least a few months after treatment, since exposure to this drug may harm the fetus. Talk with your doctor about this.

Because it is given as a shot, fulvestrant may cause bleeding in the muscle if given to women who have bleeding problems, low platelet counts, or who are on drugs like warfarin (Coumadin) to stop blood from clotting.

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.


  • nausea
  • feeling listless or tired*
  • weight gain

Less common

  • vomiting
  • constipation*
  • diarrhea
  • headache
  • abdominal (belly) pain
  • back pain
  • hot flashes
  • sore throat
  • shortness of breath
  • bleeding or pain at the site where the shot is given*


  • pain in the chest or pelvis
  • flu-like syndrome with fever, chills, and muscle and joint aches
  • swelling of the hands and feet
  • high calcium levels in women with breast cancer that has spread to bones, with symptoms such as feeling tired, poor appetite, pain, unusual thirst, increased urination, constipation, or nausea and vomiting*
  • allergic reactions with hives (skin welts), and swelling of the face, mouth, or throat

*See "Precautions" section for more detailed information.

There are some 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 2002.

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: 02/11/2010
Last Revised: 02/11/2010