Faslodex — fulvestrant

Fulvestrant is a highly selective estrogen receptor antagonist (also classified as an estrogen receptor downregulator). It exerts its action in the body not by targeting the production of estrogen, but by preventing it from exerting activity in the body. It does this by binding available estrogen receptors in a competitive manner, making them unavailable for circulating estrogens. This mode of action is very similar toNolvadex (tamoxifen citrate) andClomid (clomiphene citrate), although unlike these two agents fulvestrant does not have mixed agonist/antagonist properties. It is a pure estrogen receptor antagonist. This agent also stands out as the first injectable estrogen antagonist to catch the attention of the athletic/bodybuilding world. Although not widely used here, when applied it may be an effective drug for mitigating the side effects of excess estrogen caused by anabolic/androgenic steroid use such as gynecomastia, fat buildup, and increased water retention. Fulvestrant is very potent as an anti-estrogen, significantly more so than earlier medications likeNolvadex andClomid. Although it targets estrogen at its receptor and not its production, it can still produce an environment of low estrogenicity on par with strong aromatase inhibition. One study, for example, shows fulvestrant to be as effective inArimidex in treating breast cancer patients who have already failed with first line endocrine treatments. Another shows the drug prevents tumor cell turnover and growth significantly more effectively thantamoxifen citrate. Studies investigating the physiological response to fulvestrant note that the drug actually downregulates estrogen receptor concentrations. Furthermore, it also tends to downregulate progesterone receptor concentrations. Fulvestrant does not cross the blood brain barrier, and for this reason is believed to produce fewer neurological side effects related to estrogen antagonism such as hot flashes, mood alterations, and low energy.

Brand name Faslodex, Fulvestrant

Fulvestrant History

Fulvestrant was developed by AstraZeneca. It was approved as a prescription drug in the U.S. in 2002, and is sold under the Faslodex brand name. The drug is indicated for the treatment of estrogen receptor positive breast cancer with disease progression following traditional anti-estrogen therapy (such as tamoxifen). AstraZeneca has since expanded the market for Faslodex to include over one dozen countries, including Argentina, Belgium, Brazil, Denmark, Finland, France, Germany, Greece, Ireland, Israel, Italy, Netherlands, Norway, Poland, Portugal, Spain, Sweden, Switzerland, United Kingdom, and Venezuela.

How is Fulvestrant supplied

Faslodex (fulvestrant) is supplied in pre-filled syringes containing 50-mg/mL fulvestrant, either as a single 5 mL or two 2.5 mL injections. The product must be refrigerated for storage.

Structural Characteristics of Fulvestrant

Fulvestrant is an estrogen receptor antagonist. It has the chemical designation 7-alpha-[9- (4,4,5,5,5-penta fluoropentylsulphinyl)nonyl]estra-1,3,5-(10)- triene-3,17- beta-diol.

Fulvestrant Side Effects

The most common side effects associated with fulvestrant include gastrointestinal disturbances such as nausea, vomiting, constipation, abdominal pain, and diarrhea. Other common adverse effects include headache, back pain, hot flashes, and sore throat. Less common side effects include rash, loss of strength, urinary-tract infections, venous thromboembolism, liver enzyme elevations, vaginal bleeding, muscle pain, and low white blood cell count. Injection side reactions may also occur. Anti-estrogens can harm the development of an unborn fetus, and should never be taken during pregnancy. When taken by men (as an off-label use) to reduce estrogenicity during prolonged periods of steroid treatment, a pure estrogen antagonist may increase cardiovascular disease (CVD) risk by retarding some beneficial properties of estrogen on cholesterol values. This may include a suppression of HDL (good) cholesterol values greater than that induced by steroid therapy alone.

Fulvestrant Administration

Fulvestrant is FDA approved for the treatment of hormone receptor positive metastatic breast cancer in postmenopausal women with disease progression following anti-estrogen therapy. The recommended dose is 250 mg administered intramuscularly (buttock) per month, as either a single 5 mL injection or two 2.5 mL injections.

When used (off-label) to mitigate the estrogenic side effects of anabolic/androgenic steroid use, male athletes and bodybuilders may find a similar dose to be beneficial.

Fulvestrant Availability

Fulvestrant is available in more than one dozen countries. At the present time, all fulvestrant in circulation is likely to be of the Faslodex brand name. The drug itself is exceedingly expensive, and as a result is not widely traded on the black market.


Wlliam Llewellyn (2011) - Anabolics

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