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Fulvestrant (Faslodex®)

Last Modified: August 21, 2011

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

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. If you continue to have nausea or vomiting, notify your doctor or nurse so they can help you manage this side effect. Read the Nausea & Vomiting Tip Sheet for more suggestions.

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 studied, including clonidine (a blood pressure medication), some low dose antidepressants (such as venlafaxine and Prozac), and gabapentin. Non-medical recommendations include: keeping well-hydrated with eight glasses of water daily, wearing all-natural fiber clothes, dressing in layers, exercising on a regular basis (generally walking exercise is best), practicing relaxation exercises, and avoiding triggers such as warm rooms, spicy foods, caffeinated beverages, and alcohol.

Muscle or Joint Pain/Aches and Headache

Your doctor or nurse can recommend medication and other strategies to relive pain. Also view OncoLink's page on pain management.

Blood Clots

Blood clots are a rare side effect that can occur anywhere in the body. They occur most frequently in the calves or the lungs. Women at risk for developing blood clots include those with a family history of blood clots, smokers, those who have an inactive lifestyle, older women, and those with other medical problems. Women with any one of these risk factors may want to consider another therapy that does not have this side effect.

Signs of a blood clot in the leg may include any of the following: leg pain, warmth, swelling of one leg more than the other. Signs of a blood clot in the lung could include: fever, shortness of breath that comes on you very quickly, racing heart, chest pain (that tends to be worse when you take a deep breath).

If you have any of these signs or symptoms of blood clots, you will need to be seen immediately so that you can be treated. Blood thinners can be given. Call your doctor or nurse.

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 physician.