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Fulvestrant (Faslodex®)

OncoLink Team
Last Modified: November 2, 2015

Pronounced: ful-VES-trant

Classification: Estrogen Receptor Antagonist

About Fulvestrant

Fulvestrant works by blocking estrogen receptors in breast tissue. While estrogen may not actually cause breast cancer, it is necessary for the cancer to grow in some breast cancers. With estrogen blocked, the cancer cells that feed off estrogen may not be able to survive. Fulvestrant is considered a pure anti-estrogen because it does not stimulate estrogen receptors outside of the breast tissue. Because of fulvestrant's unique ability, it offers an option for women who have shown resistance to tamoxifen or other hormonal therapy.

How to Take Fulvestrant

Fulvestrant is given by intramuscular (into a muscle) injection. Because of the dose, it is necessary to give it in two injections. You are given the first dose, then another in 2 weeks and again in 2 more weeks, then once a month.

Possible Side Effects of Fulvestrant

There are a number of things you can do to manage the side effects of fulvestrant. Talk to your doctor or nurse about these recommendations. They can help you decide what will work best for you. These are some of the most common side effects:

Nausea and/or Vomiting

Talk to your doctor or nurse so they can prescribe medications to help you manage nausea and vomiting. In addition, dietary changes may help. Avoid things that may worsen the symptoms, such as heavy or greasy/fatty, spicy or acidic foods (lemons, tomatoes, oranges). Try antacids, (e.g. milk of magnesia, calcium tablets such as Tums), saltines, or ginger ale to lessen symptoms.

Call your doctor or nurse if you are unable to keep fluids down for more than 12 hours or if you feel lightheaded or dizzy at any time.

Hot Flashes

There are a few things you can do to help with hot flashes. Several medications have been shown to help with symptoms, including clonidine (a blood pressure medication), low doses of certain antidepressants (such as venlafaxine and Prozac), and gabapentin. Non-medical recommendations include:

  • Keep well-hydrated with eight glasses of water daily.
  • Drink ice water or apply an ice pack at the onset of a hot flash.
  • Wear cotton or lightweight, breathable fabrics and dress in layers so you can adjust as needed.
  • Exercise on a regular basis.
  • Try practicing meditation or relaxation exercises to manage stress, which can be a trigger.
  • Avoid triggers such as warm rooms, spicy foods, caffeinated beverages, and alcohol.

Weakening of the Bones (Osteoporosis)

Your doctor will check your bone health before starting therapy. This is done with a bone density scan (dexa scan). Women with no weakening of bones prior to aromatase inhibitor therapy will have a follow-up scan around one year after starting therapy, and then every one to two years.

If the scan shows that you already have some bone weakening, your doctor may order a type of medication called a bisphosphonate or calcium and vitamin D supplements to help strengthen the bones. These therapies have been shown to protect the bones from bone loss in women taking aromatase inhibitors. If the bone density remains stable, scans can then be done every two years. In addition, weight bearing exercise and a healthy diet rich in calcium and vitamin D can help protect bone health.

Muscle, Bone or Joint Pain/Aches

Your doctor or nurse can recommend medication and other strategies to relieve pain.

Injection Site Reactions

You may have pain, redness, or swelling at the site of the injection.


There are several things you can do to prevent or relieve constipation. Include fiber in your diet (fruits and vegetables), drink 8-10 glasses of non-alcoholic fluids a day, and keep active. A stool softener once or twice a day may prevent constipation. If you do not have a bowel movement for 2-3 days, you should contact your healthcare team for suggestions to relieve the constipation.


Fatigue is very common during cancer treatment and is an overwhelming feeling of exhaustion that is not usually relieved by rest. While on cancer treatment, and for a period after, you may need to adjust your schedule to manage fatigue. Plan times to rest during the day and conserve energy for more important activities. Exercise can help combat fatigue; a simple daily walk with a friend can help.  Talk to your healthcare team for helpful tips on dealing with this side effect.

Liver Toxicity

This medication can effect your liver function, which your healthcare provider will monitor for using blood tests. Notify your healthcare provider if you notice yellowing of the skin or eyes, your urine appears dark or brown or pain in your abdomen, as these can be signs of liver toxicity.

Vaginal Dryness

Vaginal dryness and related painful intercourse is one of the more common side effects of cancer therapy in women. Vaginal lubricants and moisturizers (longer lasting form of moisturizers) can help with these concerns. Talk to your healthcare team for more suggestions in managing this side effect.

Reproductive Concerns

Exposure of an unborn child to this medication could cause birth defects, so you should not become pregnant or father a child while on this medication. Effective birth control is necessary during treatment and for a period after treatment. Even if your menstrual cycle stops or you believe you are not producing sperm, you could still be fertile and conceive. You should consult with your healthcare team before breastfeeding while receiving this medication.

Other Concerns

Some women experienced vaginal bleeding during the first 6 weeks when they were switching from another hormone therapy to this one. If it continues, notify your healthcare provider.

This medication can increase the risk of developing a blood clot (DVT). Symptoms can include: swelling, redness or pain in an extremity, or shortness of breath. If you experience symptoms of these problems, you should contact your healthcare provider immediately or go to an emergency room.



If you have questions or concerns about the medication that you have been prescribed, please contact your healthcare team. OncoLink is designed for educational purposes only and is not engaged in rendering medical advice or professional services. The information provided through OncoLink should not be used for diagnosing or treating a health problem or a disease. It is not a substitute for professional care. If you have or suspect you may have a health problem, you should consult your health care provider.


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