Fulvestrant (Faslodex) is approved for postmenopausal women with a certain type of breast cancer, called hormone receptor-positive metastatic breast cancer. If the cancer is not responsive to tamoxifen, then fulvestrant is an option. Fulvestrant is given once a month as a shot in the gluteal muscle.

Estrogen's Role

Like the medicines tamoxifen, fulvestrant is classified as anti-estrogen therapy. These drugs are designed to treat the forms of breast cancer that are sensitive to the hormone estrogen. In such cases, there are estrogen receptors on the outside of the breast cancer cells. These receptors take in estrogen, which stimulates their growth.

Each anti-estrogen drug works by a slightly different mechanism, making it possible for these drugs to be used in sequence. This means that doctors have more weapons to fight breast cancer, and they may be able to control the cancer for a longer period of time. Tamoxifen blocks estrogen from reaching the estrogen receptor in breast cancer cells. Fulvestrant destroys estrogen receptors in breast cancer cells.

Side Effects

The most common side effects include:

• Nausea
• Vomiting
• Constipation
• Diarrhea
• Abdominal pain
• Headache
• Back pain
• Weakness
• Hot flashes
• Sore throat

Who Should Not Take Fulvestrant?

You will not be able to take fulvestrant if you:

• Are pregnant or breastfeeding
• Are allergic to any of the ingredients

Tell your doctor about any medicines, including over-the-counter medicines and herbs and supplements, before starting fulvestrant.