Faslodex (fulvestrant) is a brand-name injection that’s prescribed for certain types of breast cancer. As with other drugs, Faslodex can cause side effects, such as nausea, headache, and hair loss.

Faslodex belongs to a drug class called estrogen receptor antagonists. The drug is available in a generic version.

Read on to learn about potential common, mild, and serious side effects of Faslodex. For a general overview of the drug, including details about its uses, see this article.

Faslodex can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Faslodex in clinical trials:

  • bone pain
  • joint pain
  • pain at the injection site*
  • nausea*
  • headache*

* For more information about this side effect, see “Side effect specifics” below.

Mild side effects can occur with Faslodex use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to Faslodex’s prescribing information.

Mild side effects that have been reported with Faslodex include:

  • diarrhea
  • bone and joint pain
  • fatigue
  • pain in the arms, legs, and back
  • hot flashes
  • vomiting
  • loss of appetite
  • muscle pain or weakness
  • cough
  • urinary tract infection (UTI)
  • shortness of breath
  • rash
  • dizziness
  • fever
  • hair loss*
  • headache*
  • constipation*
  • injection site pain*
  • nausea*
  • mild allergic reaction†

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking Faslodex and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.
† An allergic reaction is possible after using Faslodex. However, it’s not clear whether this side effect occurred in clinical trials. To learn more, see the “Side effect specifics” section below.

Faslodex may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to Faslodex’s prescribing information.

If you develop serious side effects while taking Faslodex, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects that have been reported and their symptoms include:

  • Bleeding. Symptoms can include:
    • bleeding that is difficult to stop after getting a cut
    • bruising that happens more easily than is typical
  • Increased liver enzymes (a marker of liver injury). Symptoms can include:
    • urine that is darker in color than is typical
    • jaundice
    • pain in your abdomen
  • Anemia (low red blood cell level). Symptoms can include:
    • shortness of breath
    • weakness
    • cold hands and feet
  • Nerve pain near the injection site.
  • Severe allergic reaction.*

* An allergic reaction is possible after using Faslodex. However, it’s not clear whether this side effect occurred in clinical trials. To learn more, see the “Side effect specifics” section below.

Faslodex may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Can Faslodex cause long-term side effects?

It’s possible.

Faslodex is an injection that’s typically given in the buttocks or hip area. Rarely, some people have reported nerve pain, sciatica, and tingling in the hands and feet after a Faslodex injection. Sometimes, these nerve problems are long term.

Talk with your doctor if you have concerns about long-term side effects with Faslodex.

How long do side effects of Faslodex typically last?

It depends. In most cases, side effects of Faslodex are mild and go away after a few days or weeks. However, others, such as injection site pain, may occur each time you receive a dose. Nerve pain near the injection site may last even after you stop treatment with the drug.

If you experience side effects that do not go away or are bothersome, talk with your doctor.

Learn more about some of the side effects that Faslodex may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Faslodex.

Hair loss

In Faslodex’s clinical trials, hair loss was reported. It was more commonly reported when other drugs were used in combination with Faslodex, such as palbociclib (Ibrance), ribociclib (Kisqali), or abemaciclib (Verzenio).

Symptoms of hair loss can include:

  • thinning hair
  • more hair in your brush or comb
  • receding hairline or bald spots

What you can do

Avoiding the following during treatment with Faslodex may help to slow hair loss:

  • heat tools
  • harsh shampoos or styling products
  • rough brushing or combing of your hair

If you have concerns about hair loss while receiving Faslodex, talk with your doctor.

Injection site pain

In clinical trials of Faslodex, injection site pain was a commonly reported side effect. Symptoms can be mild or severe and include:

  • mild pain
  • swelling or discoloration
  • bruising
  • rash
  • itchiness
  • sciatica
  • nerve pain
  • tingling in the hands and feet

What you can do

For mild discoloration or swelling after an injection, you can try using a cold compress. If you experience nerve pain, tingling in the hands and feet, or sciatica, talk with your doctor know right away. Your doctor may recommend using a different injection site or switching medications.

Nausea

Nausea was commonly reported in clinical trials of Faslodex. Symptoms can include:

  • sweating
  • feeling like you are going to vomit
  • dry heaves
  • pain or pressure in your throat or stomach
  • loss of appetite

What you can do

To help with nausea, you can try:

  • eating smaller meals
  • sipping on cold beverages
  • avoiding exercise after eating
  • avoiding greasy, fried foods

Talk with your doctor if your nausea gets worse or causes you to vomit frequently. They may suggest other tips or medications to help manage this side effect.

Constipation

In clinical trials of Faslodex, constipation was commonly reported. Symptoms can include:

  • fewer than three bowel movements per week
  • stools that are hard, dry, or lumpy
  • pain during bowel movements

What you can do

To help ease constipation, you can try:

  • staying hydrated
  • eating foods that are high in fiber
  • getting regular exercise, such as walking

Talk with your doctor if you have constipation that does not improve on its own. They may recommend certain medications, such as a stool softener or a laxative, to help with this side effect.

Headache

Headache was commonly reported in clinical trials of Faslodex. Symptoms can include:

  • pain in your neck or face
  • pain that feels like a band around your head
  • dull or throbbing pain in your head

What you can do

To help ease a headache, you can try:

  • applying warm compresses or ice packs
  • laying down in a dark, quiet room
  • gently massaging the forehead or neck

If you have frequent, painful headaches, talk with your doctor. They may recommend certain medications, such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin), to help manage your headache.

Allergic reaction

As with most drugs, Faslodex can cause an allergic reaction in some people. However, it’s not clear whether this side effect occurred in clinical trials.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Faslodex. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Be sure to talk with your doctor about your health history before you take Faslodex. This drug may not be the right treatment for you if you have certain medical conditions or other factors that affect your health. These are considered drug-condition or drug-factor interactions. The conditions and factors to consider include:

Allergic reaction. If you’ve had an allergic reaction to Faslodex or any of its ingredients, your doctor will likely not prescribe Faslodex. Ask your doctor what other medications may be better options for you.

Bleeding disorder. You may have an increased risk of bleeding if you receive Faslodex injections and:

Let your doctor know about any issues you may have that affect your blood. They’ll decide whether Faslodex is safe for you.

Liver problems. If you have certain liver problems, such as liver failure, you may need a lower dosage of Faslodex. Let your doctor know about any liver problems you may have. They may order blood tests to check your liver function before you start treatment with Faslodex.

Alcohol with Faslodex

There are no known interactions between Faslodex and alcohol.

However, drinking alcohol can cause liver problems. And if you have liver problems, you may need a lower dosage of Faslodex.

If you drink alcohol, talk with your doctor if you have questions about how much, if any, alcohol is safe for you to consume while taking Faslodex.

Pregnancy and breastfeeding while taking Faslodex

In animal studies, Faslodex caused fetal harm. For this reason, Faslodex is not safe to use in pregnancy. It’s also recommended to use birth control while receiving Faslodex and for 1 year after your last dose.

It’s not known whether Faslodex passes into human breast milk. In animal studies, Faslodex was found in breast milk. For this reason, breastfeeding should be avoided while taking Faslodex and for 1 year after the last dose.

If you are pregnant, can become pregnant, are breastfeeding, or are planning to breastfeed, talk with your doctor. They may recommend a different treatment option for you.

Like other drugs, Faslodex can cause side effects. Most are mild and go away after a few days or weeks. However, some are serious. If you’d like to learn more about Faslodex, talk with your doctor or pharmacist. They can help answer any questions you have about side effects from taking the drug.

Besides talking with your doctor, you can do some research on your own. These articles might help:

  • More information about Faslodex. For details about other aspects of Faslodex, refer to this article.
  • Drug comparison. To learn how Faslodex compares with Femara, read this article.
  • A look at breast cancer. For details about breast cancer, see our breast cancer hub.

Disclaimer: Medical News Today 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.