What is Fulvestrant?

Fulvestrant (Faslodex) is a chemotherapy medication that blocks the estrogen receptor. It is used to treat metastatic breast cancer. It is also used to treat advanced breast cancer, in combination with other anti-hormonal medications; however, this is non-FDA approved and off-label. This medication blocks estrogen from binding to receptors on tumor cells and other tissue targets. Without estrogen binding the receptors, the signal to make more receptors is not transmitted. Thus, estrogen receptors are no longer produced and the tumor is prevented from growing.

How it is administered:

Fulvestrant is administered as a two intramuscular injections, one in each butt cheek. Each injection is administered slowly, over 1 to 2 minutes. The first several injections are 15 days apart. After that, fulvestrant is administered once per month.

What to expect:

Fulvestrant is commonly associated with pain at the injection site(s). Additional side effects include: hot flashes, fatigue, increases in liver enzymes, weight gain, nausea, back pain, constipation, lack of appetite and headache. Side effects that need to be reported to a provider immediately (and may require urgent medical care) include: wheezing, chest tightness, bluish skin coloration, vaginal bleeding, swelling of face, lips, tongue or throat and seizures.