Fulvestrant (Faslodex) is an estrogen receptor antagonist, or ERA, a class of medicine that stops the activity of estrogen on cancer cells to keep them from growing.

How fulvestrant works

Fulvestrant blocks the effect of estrogen that drives cancer growth in hormone receptor-positive breast cancer.

Who gets fulvestrant

Fulvestrant is FDA approved for use in postmenopausal women with metastatic hormone receptor-positive breast cancer. It may be given

  • to postmenopausal women, if the cancer is HER2-negative and they have not received hormonal therapy
  • to postmenopausal women, if the cancer grew while taking a different hormonal therapy
  • to anyone, with palbociclib (Ibrance) or abemaciclib (Verzenio) whose cancer grew despite treatment with a different hormonal therapy for early or metastatic breast cancer

How fulvestrant is given

Fulvestrant is given by injection into the buttocks. For the first month, you will receive two shots every 2 weeks. Afterward, it is given as two injections every 4 weeks.

Side effects and things to remember

Common side effects of fulvestrant are:

You should not take fulvestrant if you are pregnant, and you should not become pregnant while taking it or for a year after treatment ends as fulvestrant can harm the fetus. You also should not breastfeed while taking fulvestrant.


Reviewed and updated: January 26, 2018

Reviewed by: Jennifer Winn MD, MS


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