Faslodex (fulvestrant) is a prescription drug that’s used to treat hormone receptor (HR)-positive breast cancer. The drug comes as a liquid solution inside a prefilled syringe for injection. It’s usually given once per month.

Faslodex is prescribed for the treatment of breast cancer in adult females.* It’s a kind of hormone therapy. It may be given alone or together with other medications.

Faslodex may be used to slow or stop the growth and spread of:

Whether Faslodex is the right treatment for you depends on several additional factors, including whether you’ve had prior hormone therapy or gone through menopause.

The active ingredient in Faslodex is fulvestrant. (An active ingredient is what makes a drug work.)

This article describes the dosages of Faslodex, as well as its strength and how to take it. To learn more about Faslodex, see this in-depth article.

* We use the term “female” in this article to refer to a person’s sex assigned at birth. To learn more about differences between sex and gender, see this article.
† Advanced breast cancer means the cancer has spread to other areas near the breast, such as the lymph nodes. Metastatic breast cancer means the cancer has spread to other parts of your body.

This section describes the usual dosage of Faslodex. Keep reading to learn more.

What is Faslodex’s form?

Faslodex comes as a liquid solution inside a prefilled syringe for injection into a muscle.

What strength does Faslodex come in?

Faslodex comes in one strength: 250 milligrams (mg) per 5 milliliters (mL).

What is the usual dosage of Faslodex?

The information below describes dosages that are commonly used or recommended. Your doctor will determine the best dosage to fit your needs.

Dosage for breast cancer

The usual dose of Faslodex is 500 mg. Each prefilled syringe contains 250 mg of Faslodex. You’ll receive two injections, one into the muscle of each buttock, to total 500 mg.

During your first month of treatment with Faslodex, you’ll receive three doses of 500 mg. These doses will be given on days 1, 15, and 29.

Following this, the typical dosage is 500 mg once per month (approximately every 28 days).

Is Faslodex used long term?

Faslodex may be given long term if it’s working well. Faslodex should slow or stop breast cancer growth. If your cancer is not growing in size or spreading, and you don’t have serious side effects from Faslodex, you may be prescribed the medication long term.

If you have questions about the long-term use of Faslodex, talk with your doctor.

Dosage adjustments

If you have liver problems, your doctor may adjust your dosage of Faslodex.

The liver helps to break down Faslodex. If your liver doesn’t work as well as it should, it may not break down Faslodex as efficiently. This can lead to higher levels of Faslodex in your body. And this increases your risk of side effects.

If you have moderate liver disease, your doctor will lower your dose of Faslodex. Instead of 500 mg, you’ll receive a lower dose of 250 mg. You’ll receive 250 mg on days 1, 15, and 29 during your first month of treatment, followed by 250 mg once per month.

If you have questions about a possible dosage adjustment of Faslodex, talk with your doctor.

Faslodex comes as a liquid solution inside a prefilled syringe. It’s given as an injection into a muscle.

Each syringe contains 250 mg of Faslodex. The typical dose is 500 mg. To receive 500 mg, you’ll be given two injections, one into the muscle of each buttock.

The injections are given by a healthcare professional at your doctor’s office. For each injection, the liquid solution will be slowly injected over 1–2 minutes.

If you have any questions about what to expect during your Faslodex treatment, talk with your doctor.

If you miss an appointment to receive your dose of Faslodex, call your doctor’s office as soon as you remember to reschedule.

If you need help remembering your appointments, try setting a medication reminder. This can include setting an alarm or downloading a reminder app on your phone.

The sections above describe the usual dosage provided by the drug’s manufacturer. If your doctor recommends Faslodex for you, they’ll prescribe the dosage that’s right for you.

Talk with your doctor if you have questions or concerns about your current dosage.

Here are some examples of questions you may want to ask your doctor:

To learn more about Faslodex, see these articles:

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.