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What is Faslodex® ? (fulvestrant)

Faslodex is an estrogen receptor antagonist used to treat certain cases of hormone receptor positive (HR+) advanced or metastatic breast cancer. It is approved to treat: 1,2

  • HR+, human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer in women who are postmenopausal and have not been previously treated with endocrine therapy
  • HR+ advanced breast cancer in women who are postmenopausal and whose disease has progressed after treatment with other endocrine therapy
  • HR+, HER2- advanced breast cancer or breast cancer that has metastasized (spread to other parts of the body) in combination with Verzenio™ (abemaciclib) or Ibrance® (palbociclib) in women whose disease has progressed after treatment with other endocrine therapy
  • HR+, HER2- advanced breast cancer or breast cancer that has metastasized (spread to other parts of the body) in women who are postmenopausal, in combination with ribociclib as initial endocrine therapy or in women whose disease has progressed after treatment with other endocrine therapy

Fulvestrant is manufactured by AstraZeneca.

What is the ingredient in Faslodex?

The active ingredient in Faslodex is fulvestrant, an estrogen receptor antagonist.1

How does fulvestrant work?

Many breast cancers have estrogen receptors on the surface of their cells. Estrogen can connect to these receptors and stimulate the growth of these breast cancers. Fulvestrant binds to the estrogen receptor and can help block or slow the breast cancer’s growth.1

What are some of the possible side effects of fulvestrant?

The most common side effects experienced by patients receiving fulvestrant in clinical trials included:1,2

  • Injection site pain
  • Nausea
  • Joint, muscle, or bone pain
  • Headache
  • Back pain
  • Fatigue or weakness
  • Pain in the arms or legs
  • Hot flashes
  • Vomiting
  • Loss of appetite
  • Cough
  • Shortness of breath
  • Constipation
  • Diarrhea
  • Increases in liver enzymes

In some people, fulvestrant may cause a hypersensitivity reaction (severe allergic reaction), potentially causing itching, hives, difficulty breathing, or swelling of the face, lips, tongue, or throat.2

Fulvestrant may cause nerve damage where it is injected (in the buttocks), which may cause numbness, tingling, and/or weakness in the legs. These symptoms should be reported to a healthcare professional.2

Things to know about fulvestrant

Before starting treatment with fulvestrant, patients should discuss with their doctor all their health conditions, especially:2

  • Any liver problems
  • Problems with bleeding and/or low platelet levels in the blood
  • If patients are pregnant, or planning to become pregnant
  • If patients are breastfeeding, or planning to breastfeed

Fulvestrant may cause harm to an unborn baby and should not be used by women who are pregnant. Women who can become pregnant should use effective contraception during fulvestrant treatment and for at least one year after their final dose.2

It is not known if fulvestrant can pass into breastmilk. Women should not breastfeed during treatment with fulvestrant and for at least one year after their final dose of fulvestrant.2

Before starting treatment with fulvestrant, patients should talk to their doctor about all their medications (prescription and over-the-counter), herbal supplements, and vitamins they are taking. Some of these may affect the way fulvestrant works, or fulvestrant may affect how other medicines work.2

Dosing information

Fulvestrant is given as an intramuscular (into the muscle) injection into the buttocks. The recommended dose is 500 mg given slowly (1-2 minutes per injection) as two injections, one in each buttock, on days 1, 15, and 29 of treatment and then once monthly.1

In women with liver impairment, the dose may be reduced to 250 mg as one injection given in the buttock on days 1, 15, and 29 of treatment and then once monthly.1

For more information, read the full prescribing information of fulvestrant.

Patients should talk to their doctor if they have any questions, or if they have questions regarding their fulvestrant regimen.

Written by: Editorial Team | Last reviewed: October 2019.
  1. Faslodex prescribing information. AstraZeneca. Available at https://www.azpicentral.com/faslodex/faslodex.pdf. Accessed 9/20/18.
  2. Faslodex product website. AstraZeneca. Available at https://www.faslodex.com/. Accessed 9/20/18.