Faslodex (Fulvestrant): Uses, Side Effects, Dosage, FAQs

Faslodex is the brand name for Fulvestrant. Faslodex belongs to a class of hormone therapy drugs. It fights cancer as an “estrogen receptor Antagonist.”

Faslodex is a liquid given once a month as an injection into a muscle, usually at your doctor’s office.

AstraZeneca manufactures Faslodex for the treatment of metastatic hormone receptor-positive breast cancer.

Faslodex Uses

Faslodex injection is used to treat breast cancer spread to other parts of the body in postmenopausal women. It is used in the treatment and prevention of the following conditions.

  • It is used in Hormone receptor (HR)-positive advanced breast cancer, women who have gone through menopause and whose disease has progressed after antiestrogen therapy.
  • It is also used in 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.
  • It is used in combination with palbociclib (Ibrance)  or abemaciclib in treating HR-positive, HER2-negative advanced breast cancer or breast cancer that has spread to other parts of the body (metastatic).
  • Faslodex does not work on hormone-receptor-negative breast cancer.

Mechanism Of Action

The female sex hormones estrogen and progesterone stimulate the growth of certain breast cancers. These breast cancers are called hormone-sensitive or hormone receptor-positive.

Drugs that block these hormones’ actions can slow down or stop the growth of breast cancer cells.

Faslodex prevents estrogen from reaching cancer cells by blocking estrogen receptors and reducing the number of cancer cell receptors. It binds, blocks, and increases the degradation of the estrogen receptor.

Faslodex Side Effects

The most common side effects of Faslodex are:

  • Nausea
  • Vomiting
  • Diarrhea
  • Hot flashes
  • constipation
  • Stomach/abdominal pain
  • injection site pain
  • sore throat
  • back pain
  • headache

Some women may have other side effects while taking Faslodex:

  • Dizziness
  • Bone/joint pain
  • Swelling
  • loss of appetite
  • Dry skin.
  • Sweating
  • Sleeping problems
  • Nervousness/anxiety


Before using this injection, tell your doctor or pharmacist if you are/have

  • Allergic to it; or if you have any other allergies.
  • Faslodex may make you dizzy. Do not drive, use machinery, or do any activity that requires alertness until you can safely perform such activities.
  • Liver disease, bleeding problems, and low platelet counts (thrombocytopenia).
  • Pregnant or plan to become pregnant. It would help if you did not become pregnant while using fulvestrant. Fulvestrant may harm an unborn baby.
  • Do not breastfeed while taking this medication.


Faslodex Injection is contraindicated in patients with known hypersensitivity to the drug or any of its components. Hypersensitivity reactions, including

  • Angioedema
  • Urticaria and
  • Redness of the face,

Other symptoms include

  • Dizziness,
  • A headache,
  • shortness of breath and
  • Anxiety.


The recommended dose is 500 mg by intramuscular route in the buttocks. Inject it slowly for 1 to 2 minutes.

There are two injections of 5 ml each, one in each buttock on days 1, 15, and 29, then once a month.

When used in combination with palbociclib (Ibrance), the recommended dose is 500 mg intramuscularly slowly in the buttocks. Inject it slowly for 1 to 2 minutes.

There are 2 injections of 5 ml on days 1, 15, and 29, and once a month since then.

The recommended dose of palbociclib is a 125 mg capsule once a day for 21 consecutive days, followed by a rest period of 7 days, including a full cycle of 28 days. Palbociclib should be taken with a meal.

Frequently Asked Questions (FAQS)

1. What is the Faslodex Injection?

It is the Brand/Trade name for Fulvestrant. It belongs to a class of hormone therapy drugs.  It fights cancer as an “estrogen receptor down-regulator.”

2. What Faslodex is used for?

Faslodex Injection treats certain types of breast cancer in post-menopausal women that have spread to other areas of the body.

3. How to Use it?

This medicine is slowly injected into the gluteal muscle as directed by your doctor. It is usually given every 2 weeks for the first 3 doses and then monthly. You will be asked if you want to give your dose in one or two injections.

4. What happens if I overdose on Faslodex?

Since a healthcare professional administers this drug in a medical setting, it is unlikely to overdose. If an overdose is suspected, contact a poison control center or the emergency room immediately.

5. What other drugs will affect Faslodex?
Tell your doctor about all your other prescriptions and over-the-counter medications, especially:

According to a study published in the Journal “Of British Pharmacological Society,” the addition of fulvestrant to anastrozole treatment decreased the trough anastrozole concentration.

This is not a complete list of drug interactions. Consult your doctor before using other medications with Faslodex.

6. What are the side effects of Faslodex Injection?

Common side effects associated with the use of this medicine include;  nausea, vomiting, diarrhea, hot flashes, constipation, stomach/abdominal pain, sore throat, back pain, headache, and injection site pain. Check more above.

7. Is Faslodex a form of Chemotherapy?

Faslodex is a targeted therapy that keeps estrogen from forming more cancer cells.

8. Is Faslodex Safe to use during Pregnancy?

You should not receive fulvestrant if you are pregnant. Avoid becoming pregnant for at least one year after stopping this medication. The use of fulvestrant during pregnancy can harm the fetus. Use effective contraception to prevent pregnancy using this medication and at least one year after the treatment.

9. Is Faslodex safe while breastfeeding?

It is not known if Fulvestrant enters breast milk or could harm the baby. You should not receive fulvestrant while breastfeeding. Avoid breastfeeding for at least one year after stopping this medication. Ask your doctor.

10. Can I drive or use machines after taking Faslodex?

This medicine may make you feel dizzy. Do not drive, operate machinery, or perform activities requiring alertness until you can safely perform them.

11. How is it stored?

Supplied in two 5 ml clear glass containers (type 1), each containing 250 mg / 5 ml Intramuscular solution, with a tamper-evident cap.

12. Who can not take this medicine?

Do not use this medicine if you are allergic to fulvestrant or any of the other ingredients. Do not use it during pregnancy and lactation.

13. How do you inject Faslodex?

Displaces excess gas from the syringe (possibly leaving a small bubble of gas behind). Then slowly Inject intramuscularly (1-2 minutes/injection) into the buttocks (gluteal area).

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