Fulvestrant is a hormone therapy you may be prescribed if you have certain types of breast cancer. Fulvestrant is an estrogen receptor antagonist that binds to estrogen receptors in breast cancer cells. The hormone estrogen encourages breast cancer cells to grow and fulvestrant works by binding and blocking the estrogen receptor, which slows the growth of cancer.

Fulvestrant was first approved by the FDA in 2002 after Phase 3 trials showed that the patients on fulvestrant took longer for their cancer to get worse, when compared to patients on Arimidex (anastrozole). It is approved to be used for certain types of breast cancer in women, so your doctor will only prescribe it for you if it has been shown to be effective for your type of cancer.

It is given as an injection into your buttock muscle once a month, but your dose may change depending on how well it is working for you and if you are having side effects. You may also be given other medicines with fulvestrant to treat your breast cancer.

What is fulvestrant used for?

Fulvestrant is a prescription medicine used to treat advanced breast cancer or breast cancer that has spread to other parts of the body (metastatic).

Fulvestrant may be used alone, if you have gone through menopause, and your advanced breast cancer is:

• hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative and has not been previously treated with endocrine therapy
  or
• HR-positive and has progressed after endocrine therapy.

Fulvestrant may be used in combination with ribociclib, if you have gone through menopause, and your advanced or metastatic breast cancer is HR-positive and HER2-negative, and has not been previously treated with endocrine therapy or has progressed after endocrine therapy.

Fulvestrant may be used in combination with palbociclib or abemaciclib if your advanced or metastatic breast cancer is HR-positive and HER2-negative, and has progressed after endocrine therapy.

When fulvestrant is used in combination with palbociclib, abemaciclib, or ribociclib, also read the Patient Information for the prescribed product.

It is not known if this medicine; is safe and effective in children.

It is not known if fulvestrant is safe and effective in people with severe liver problems.

• Your healthcare provider will give you fulvestrant by injection into the muscle of each buttock.
• Your healthcare provider may change your dose if needed.

Fulvestrant is an intramuscular injection that is supplied as 5-mL single-dose prefilled syringes containing 250 mg/5 mL fulvestrant.

The recommended dose of fulvestrant is 500 mg to be administered intramuscularly into the buttocks (gluteal area) slowly (1 - 2 minutes per injection) as two 5 mL injections, one in each buttock, on Days 1, 15, 29, and once monthly thereafter.

Do not receive fulvestrant if you have had an allergic reaction to it or any of the inactive ingredients. See the end of this page for a list of ingredients.

Symptoms of an allergic reaction to fulvestrant may include:

• itching or hives

• swelling of your face, lips, tongue, or throat

• trouble breathing

What should I tell my healthcare provider before taking fulvestrant?

Before receiving this medicine, tell your healthcare provider about all of your medical conditions, including if you:

• have a low level of platelets in your blood or bleed easily
• have liver problems
• are pregnant, or plan to become pregnant. See below for more information on fulvestrant and pregnancy, as it can harm your unborn baby
• are breastfeeding or plan to breastfeed. Do not breastfeed during treatment with fulvestrant and for one year after the last dose. See below for more information on fulvestrant and breastfeeding.
• It is important to tell your healthcare provider if you take a blood thinner medicine.

Fulvestrant may cause serious side effects, including:

• Injection site related nerve damage. Call your healthcare provider if you develop any of the following symptoms in your legs following the injection:
  • numbness
  • tingling
  • weakness

The most common side effects of fulvestrant include:

• injection site pain
• nausea
• muscle, joint, and bone pain
• headache
• back pain
• tiredness
• pain in arms, hands, legs, or feet
• hot flashes
• vomiting
• loss of appetite
• weakness
• cough
• shortness of breath
• constipation
• increased liver enzymes
• diarrhea

Fulvestrant may cause fertility problems in males and females. Talk to your healthcare provider if you plan to become pregnant. See below for more information on fulvestrant and pregnancy.

Tell your healthcare provider if you have any side effect that bothers you or that does not go away.

These are not all of the possible side effects with this medicine. For more information, ask your healthcare provider or pharmacist.

Call your healthcare provider for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Some medications interact with fulvestrant, so it is important to tell your doctor about any medicines that you are currently taking, or if you start or stop any medicine while you are having cancer treatment. Also tell your doctor about any over-the-counter medicines, vitamins, minerals or herbal products that you take.

Especially tell your healthcare provider if you take a blood thinner medicine.

To find out more about interactions with fulvestrant click the link below: