What is Faslodex: Uses, Warnings & Interactions

Updated May 14, 2025  •  Published Dec 30, 2020

Faslodex overview

BRAND NAMES:

  • Faslodex

Generic Names:

  • Fulvestrant

Uses:

  • Treats breast cancer.

Therapeutic Classes:

  • Antiestrogen

Forms:

  • Injectable

How it’s taken:

  • By injection

What is Faslodex used for?

Faslodex is an anti-estrogen medication used to treat hormone receptor positive (HR+) and human epidermal growth factor receptor 2 negative (HER2-) breast cancer that has spread in post-menopausal women. Estrogen binds to these receptors and stimulates breast cancer cells to grow. Faslodex blocks the action of estrogen on the HR+ and HER- of breast cancer cells. The receptors change shape and stop working, causing the number of breast cancer cells to be reduced. This medication works by reducing the number of breast cancer cells. Faslodex is available as an intramuscular injection.

What form(s) does Faslodex come in

  • Injectable

What are common Faslodex doses?

  • Syringe 5ML of 250MG/5ML

Common Faslodex prescriptions

  • Faslodex
    5ml of 250mg/5ml syringe

How to take Faslodex

  • Injection routeYour doctor will prescribe your exact dose and tell you how often it should be given. This medicine is given as a shot into one of your muscles.

  • Injection routeYou will receive this medicine while you are in a hospital or cancer treatment center. A nurse or other trained health professional will give you this medicine.

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

  • Missed dose: Injection routeThis medicine needs to be given on a fixed schedule. If you miss a dose, call your doctor, home health caregiver, or treatment clinic for instructions.

  • Missed dose: Injection routeThis medicine needs to be given on a fixed schedule. If you miss a dose, call your doctor, home health caregiver, or treatment clinic for instructions.

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

  • Injection routeYou will receive this medicine while you are in a hospital or cancer treatment center. A nurse or other trained health professional will give you this medicine.

  • Injection routeYour doctor will prescribe your exact dose and tell you how often it should be given. This medicine is given as a shot into one of your muscles.

What to do if you miss a dose of Faslodex

Faslodex contraindications

  • This medicine is not right for everyone. You should not receive it if you had an allergic reaction to fulvestrant, or if you are pregnant.

Faslodex warnings

  • This medicine may increase your risk of bleeding, including vaginal bleeding.

  • Oral routeCancer medicine can cause nausea or vomiting, sometimes even after you receive medicine to prevent these effects. Ask your doctor or nurse about other ways to control any nausea or vomiting that might happen.

  • Tell your doctor if you have liver disease or a bleeding or blood disorder.

  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant. If you are a woman who can bear children, your doctor may give you a pregnancy test 7 days before you start using this medicine to make sure you are not pregnant. Use an effective form of birth control during treatment and for 1 year after your last dose of this medicine.

  • Do not breastfeed during treatment and for 1 year after your last dose of this medicine.

  • Injection routeMedicines used to treat cancer are very strong and can have many side effects. Before receiving this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.

  • This medicine could cause infertility. Talk with your doctor before using this medicine if you plan to have children.

Faslodex interactions

  • Some foods and medicines can affect how fulvestrant works. Tell your doctor if you are using a blood thinner (including warfarin).

  • Do not breastfeed during treatment and for 1 year after your last dose of this medicine.

  • Injection routeMedicines used to treat cancer are very strong and can have many side effects. Before receiving this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.

  • Tell your doctor if you have liver disease or a bleeding or blood disorder.

  • This medicine may increase your risk of bleeding, including vaginal bleeding.

  • This medicine could cause infertility. Talk with your doctor before using this medicine if you plan to have children.

  • Oral routeCancer medicine can cause nausea or vomiting, sometimes even after you receive medicine to prevent these effects. Ask your doctor or nurse about other ways to control any nausea or vomiting that might happen.

Faslodex side effects

Serious Side Effects

  • Unusual bleeding, bruising, or weakness

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing

  • Fever, chills, cough, sore throat, and body aches

Less Serious Side Effects

  • Headache, nausea

  • Sores or white patches on your lips, mouth, or throat

  • Pain, itching, burning, numbness, tingling, swelling, or a lump under your skin where the shot was given

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