Faslodex treats certain types of breast cancer in post-menopausal women that have spread to other areas of the body. Faslodex is an injectable medication that is given by a healthcare professional.

Faslodex Overview


Faslodex is a prescription medication used to treat certain types of breast cancer in post-menopausal women. Faslodex belongs to a group of drugs called estrogen receptor antagonists. It works by blocking the activity of estrogen in breast tissue which stops the cancer from growing.

This medication comes in an injectable form. It is given directly into the muscle of the buttock by a healthcare provider.

Common side effects include injection site pain, nausea, and headache.

How was your experience with Faslodex?

First, a little about yourself

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What are you taking Faslodex for?

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  • Other
  • Breast Neoplasms

How long have you been taking it?

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  • Less than a week
  • A couple weeks
  • A month or so
  • A few months
  • A year or so
  • Two years or more

How well did Faslodex work for you?

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Uses of Faslodex

Faslodex is a prescription medication used to treat certain types of breast cancer in post-menopausal women.

Faslodex is used to treat women with: 

  • Hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer, who have gone through menopause and have not been previously treated with endocrine therapy 
  • HR-positive advanced breast cancer, who have gone through menopause and whose disease has progressed after endocrine therapy
  • HR-positive, HER2-negative advanced breast cancer or breast cancer that has spread to other parts of the body (metastatic), in combination with palbociclib or abemaciclib, in women whose disease has progressed after endocrine therapy

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information. 


Faslodex Drug Class

Faslodex is part of the drug class:

Side Effects of Faslodex

Serious side effects have been reported with Faslodex. See the 'Drug Precautions' section for additional information.

Common side effects of Faslodex include:

  • injection site pain
  • nausea
  • muscle, joint, and bone pain
  • headache
  • tiredness
  • hot flashes
  • vomiting
  • loss of appetite
  • weakness
  • cough
  • constipation
  • shortness of breath
  • increased liver enzymes

This is not a complete list of Faslodex side effects. Tell your healthcare provider if you have any side effect that bothers you or does not go away.

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

Faslodex Interactions

No drug interactions have been identified by the manufacturer. However, you should tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Not all drug interactions are known or reported and new drug interactions are continually being reported.

Faslodex Precautions

Serious side effects have been reported with Faslodex including the following.

Blood disorders: Because Faslodex is administered intramuscularly, it should be used with caution in patients with bleeding diatheses (unusual bleeding tendency or disposition), thrombocytopenia, or anticoagulant use (blood thinners like Coumadin).

Hepatic Impairment: A dose reduction is recommended in patients with moderate hepatic impairment (liver problems). Faslodex has not been studied in patients with severe hepatic impairment.

Pregnancy: Women should be advised not to become pregnant while receiving Faslodex. This medicine may harm the unborn baby.

Do not take Faslodex if you are allergic to Faslodex or any of its ingredients.

Symptoms of an allergic reaction to Faslodex may include:

  •  Itching
  •  Swelling of your face, lips, tongue or throat
  •  Trouble breathing



Faslodex Food Interactions

Medicines can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of Faslodex there are no specific foods that you must exclude from your diet when receiving this medication.

Inform MD

Before you receive Faslodex, tell your doctor:

  • if you are allergic to Faslodex or any other medications
  • if you have or have ever had any bleeding problems (low level of platelets in your blood or bleed easily)
  • if you have liver disease
  • about any other medical conditions you have
  • if you are pregnant or breastfeeding

Tell your doctor about the medicines you take including prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products. 

Faslodex and Pregnancy

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Faslodex falls into category D. In animal studies, pregnant animals were given this medication and had some babies born with problems. No well-controlled studies have been done in humans, though. Therefore, this medication may be used if the potential benefits to the mother outweigh the potential risks to the unborn child.

Faslodex and Lactation

It is not known if Faslodex crosses into human milk. Because many medications can cross into human milk and because of the possibility for serious adverse reactions in nursing infants with use of this medication, a choice should be made whether to stop nursing or stop the use of this medication. Your doctor and you will decide if the benefits outweigh the risk of using Faslodex.

Faslodex Usage

Take Faslodex exactly as prescribed.

Faslodex comes in an injectable form and is usually given every 15 days at the beginning of treatment and once per month later in treatment. Your healthcare provider will give you the appropriate amount of Faslodex by injection into the muscle of your buttock. It is usually administered in a medical facility (doctor's office or hospital).

Keep all appointments with your doctor. If you miss an appointment to receive a dose of Faslodex, reschedule as soon as possible.

Faslodex Dosage

Take this medication exactly as prescribed by your doctor. Your doctor will determine the best dose and schedule for you.

Faslodex 500 mg should be administered intramuscularly into the buttocks slowly (1 - 2 minutes per injection) as two 5 mL injections, one in each buttock, on days 1, 15, 29 and once monthly thereafter.

A dose of 250 mg is recommended in patients with moderate hepatic impairment to be administered intramuscularly into the buttock slowly (1- 2 minutes) as one 5 mL injection on days 1, 15, 29 and once monthly thereafter.

Faslodex Overdose

There is no clinical experience with overdosage in humans. In studies, no adverse reactions were seen in healthy male and female volunteers who received very large intravenous (IV) doses, rather than the usual intramuscular (IM) doses.

Faslodex is usually administered by a healthcare provider in a medical setting making it unlikely for an overdose to occur. However, if you believe you or someone you know is experiencing an overdose contact your local poison control center or call 911.