Faslodex® (fulvestrant) selective estrogen receptor antagonist profile

akn · Jun 2, 2014

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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 to
Nolvadex (tamoxifen citrate) and Clomid (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 like Nolvadex and Clomid.
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 in
Arimidex in treating breast cancer patients who have already
failed with first line endocrine treatments.655 Another shows
the drug prevents tumor cell turnover and growth
significantly more effectively than tamoxifen citrate.656
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.657
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.
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 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:
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.
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 offlabel
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.
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.
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.

By Willam Llewellyn

Faslodex® (fulvestrant) selective estrogen receptor antagonist profile

akn

Musclechemistry Member

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