Pharmaceutical Name: Fulvestrant
Drug Classification: Estrogen Receptor Antagonist/Estrogen Receptor
Active Life: approximately four to five weeks
Fulvestrant is a selective estrogen receptor antagonist, or estrogen receptor
down-regulator. It is able to eliminate the action of estrogen in the body by
blocking the available estrogen receptors. So therefore unlike aromatase
inhibitors it does not prevent aromatization, but rather limits the activity
of the estrogen after it is created (1). As with most aromatase inhibitors and
selective estrogen receptor modulators the primary use of fulvestrant is in
the treatment of estrogen-dependent breast cancer. This is still what it is
predominantly used for medically now.
Fulvestrant is also quite different in its effects than selective estrogen
receptor modulators in that it does not seemingly only target receptors in
specific tissues but rather receptors located throughout most of the body.
This would indicate that it should have an effect on a plethora of estrogenic
side effects in the body, unlike selective estrogen receptor modulators such
as tamoxifen citrate which only effect certain tissues. Also unlike selective
estrogen receptor modulators fulvestrant has no agonist properties. This means
that the drug does not exhibit any estrogenic-like activity in some of the
tissues of the body. This would have to be seen as a drawback of the compound
as there is some research that indicates the estrogen-like activity of such
compounds as tamoxifen citrate or clomiphene citrate have positive effects in
the body such as increasing HDL cholesterol in users (although this is a
somewhat controversial assertion). This would also seemingly limit it's use
during post-cycle therapy as it will have little effect in raising the natural
testosterone levels in users, although no research has indicated this in the
positive or negative.
It has also been demonstrated that fulvestrant can down-regulate progesterone
receptor concentrations (2). This means that along with being able to help
decrease the estrogenic effects related to anabolic steroid use, it can also
be used in decreasing the activity of progestin, a cause for concern when
using certain compounds.
Fulvestrant is administered using intramuscular injections. For the most part
the full effects of the drug can be achieved using 250 milligrams per
injection. Due to the active life of the compound these injections only have
to be administered approximately once every four to five weeks. This is
obviously a benefit when compared to the frequent dosing schedule that is
required with aromatase inhibitors or selective estrogen receptor modulators.
At doses of 250 milligrams per month it has been shown that fulvestrant is
just as effective as one milligram per day of anastrozole (3) or 2.5
milligrams per day of letrozole (4) at reducing estrogen in the body. It has
also been demonstrated in clinical research that fulvestrant can be effective
in the treatment of some estrogen-dependent breast cancers where tamoxifen
citrate has failed (4, 5). This should indicate how powerful the compound
As is the case with most aromatase inhibitors, by effecting the action of
estrogen is nearly all of the tissues of the body fulvestrant can have a
negative effect on a user�s immune system in general and specifically, users
will no doubt notice a detrimental effect on both their HDL and LDL
cholesterol levels with this drug. So while it is true that fulvestrant does
not eliminate estrogen from the body, or eliminate aromatization, it is true
that it in fact stops most of its effects in the body, both positive and
It is also true that this elimination of the estrogenic action in the body
could lower a user�s libido, as is the case with some aromatase inhibitors.
This obviously brings up a negative aspect of the extremely long active life
of the compound. If one begins to experience any of the possible negative side
effects associated with fulvestrant a user will not be able to adjust their
dosages or cease administering the compound until it clears their system. This
can take weeks depending at what time the last injection was done. Obviously
this is something that should be taken into consideration when determining
whether or not to use this compound.
1. Cheung KL, Robertson JF. Fulvestrant. Expert Opin Investig
Drugs 2002 Feb; 11(2):303-8
2. Johnston S, Fulvestrant and the sequential endocrine cascade for advanced
breast cancer. Br J Cancer. 2004 Mar;90 Suppl 1:S15-8
3. McKeage K, Curran MP, Plosker GL. Fulvestrant: a review of its use in
hormone receptor-positive metastatic breast cancer in postmenopausal women
with disease progression following antiestrogen therapy. Drugs.
4. Bundred NJ, Anderson E, Nicholson RI, Dowsett M, Dixon M, Robertson JF.
Fulvestrant, an estrogen receptor downregulator, reduces cell turnover index
more effectively than tamoxifen. Anticancer Res. 2002 Jul-Aug;22(4):2317-9
5. Howell A, Robertson JFR, Quaresma Albano J, Aschermannova A, et al.
Fulvestrant, Formerly ICI 182, 780, Is as Effective as Anastrozole in
Postmenopausal Women with Advanced Breast Cancer Progressing After Prior
Endocrine Treatment. J Clin Oncol. 2002; 1:57
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