Faslodex

Fulvestrant is a highly selective estrogen receptor antagonist. It exerts its action in the body not by targeting the production of estrogen, but by preventing it from exerting activity on 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 to Nolvadex and Clomid, although unlike these two agent fulvestrant does not have mixed agonist/antagonist properties. It is a pure estrogen receptor antagonist. This agent also stands out as the first inject able estrogen antagonist to catch the attention of the athletic and bodybuilding world. Although not widely used here, when applied it may be 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 was developed by the pharmaceutical company AstraZeneca. It was approved as a prescription drug in the U.S in 2002, and is sold under the brand name of Faslodex. The drug is indicated for the treatment of estrogen receptor positive breast cancer with disease progression following traditional anti estrogen treatment with drugs  such as nolvadex. The company has since expanded  its market for Faslodex to include over a dozen countries worldwide.

Fulvestrant is very potent as an anti estrogen, significantly more so than earlier medications like nolvadex and clomid. Although it targets estrogen at its receptor and not its production, it can still produce an environment of low estrogencity on par with strong aromatase inhibition. One study, for example shows fulvestrant to be as effective in arimidex 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 than tamoxifen citrate. Studies investigating the physiological response to fulvestrant note that the drug actually down regulates estrogen receptor concentrations. Furthermore, it also tends to down regulate progesterone receptor concentrations. Fulvestrant does not cross the blood brain barrier, and for this reason is believed to produce fewer neurological side effects such as hot flashes, mood alterations, and low energy. The most common side  effects associated with the drug 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 unborn fetuses and should not be taken by pregnant women. The drug is most commonly supplied in pre-filled syringes containing 50mg/ ml.

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 250mg administered intramuscularly per month as a single 5ml injection or two 2.5ml 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 as is used for medical reasons to be effective for their needs.