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Fulvestrant is available as an intramuscular (IM) injection.

How It Works

Fulvestrant is called an antiestrogen medicine. This means that it blocks the effect of estrogen in the body. It is only used for postmenopausal women who have been diagnosed with estrogen receptor-positive (ER+) breast cancer.1

Why It Is Used

Fulvestrant is used to treat estrogen receptor-positive (ER+) metastatic breast cancer in postmenopausal women when other hormonal therapies, such as tamoxifen, have stopped working.

How Well It Works

Fulvestrant is as effective as aromatase inhibitors, such as anastrozole (Arimidex), in the treatment of women with metastatic breast cancer when other hormonal therapies, such as tamoxifen, have stopped working.2 It only works for post-menopausal women who have been diagnosed with estrogen receptor-positive (ER+) breast cancer.

Side Effects

Most women do not have problems with side effects while taking fulvestrant. When side effects happen, they are generally mild and may include:

  • Nausea or vomiting.
  • Constipation or diarrhea.
  • Abdominal pain.
  • Headache.
  • Back pain.
  • Hot flashes.
  • Sore throat.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Fulvestrant should be given only under the supervision of a medical oncologist. It is approved for use after menopause.

Fulvestrant is not effective before menopause. Estrogen production during menstruation is not affected by these medicines.

Further study is needed to determine how long to use fulvestrant. It hasn't been studied long enough to answer this question.

Do not take this medicine if you are or may be pregnant. Do not breast-feed while you are taking this medicine.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. National Cancer Institute (2006). Fulvestrant: New treatment option for advanced breast cancer. Available online: http://www.nci.nih.gov/clinicaltrials/results/fulvestrant0802.
  2. Abramowicz M (2005). Drugs for breast cancer. Treatment Guidelines From the Medical Letter, 3(29): 1–6.


By Healthwise Staff
Primary Medical Reviewer Joy Melnikow, MD, MPH - Family Medicine
Specialist Medical Reviewer Douglas A. Stewart, MD - Medical Oncology
Specialist Medical Reviewer Brian D. O'Brien, MD - Internal Medicine
Last Revised October 20, 2009

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.