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Pharmaceutical Name: Fulvestrant Drug Classification: Estrogen Receptor Antagonist/Estrogen Receptor Down-Regulator 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. Use/Dosing 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 truly is. Risks/Side Effects 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 negative. 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. References 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. 2004;64(6):633-48 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 |