Arimidex

[Antò]

(Anastrozole)

Arimidex (Anastrozole) is what we call an aromatase inhibitor (AI). In clinical use, it´s used to halt the progression of Breast Cancer in women. It works by blocking the aromatase enzyme, which is responsible for the production of estrogen. In athletics and bodybuilding, it is used as an ancillary compound to be added to a cycle of Anabolic Steroids. In this respect it is also used for its estrogen reducing properties, but it has the additional benefit of increasing testosterone levels, as we´ll see...
Arimidex Side Effects

Many anabolic steroids aromatize (convert to estrogen via the aromatase enzyme), and this is responsible for many of the unwanted side effects found with anabolic steroid use (acne, gynocomastia, water-retention, etc...). In one study, both .5mg and 1mg doses of Arimidex were shown to decrease estrogen by roughly 50%. The 1mg/day dose also increased testosterone levels by 58% (1). In that same study, in both groups, LH and FSH also went up slightly.
Take a look:

Changes in testosterone and E2 concentrations in normal young men (15 22 yr old) before () and after 10 days of oral anastrozole at 0.5 and 1 mg.(1)
This would seem to suggest that for use during a cycle, a dose of .5mgs/day would be sufficient to combat estrogen-related side effects. It is, however, important to remember that some estrogen is necessary to obtain optimal muscle growth. The lower estrogen levels provided by ´dex seems, anecdotally at least, to produce a more "hard" and "quality" look for bodybuilders who have experimented with it´s use in either a cutting or bulking cycle.
I´d like to point out that the elevation in Testosterone provided by Arimidex is so large that it can be used as a "form" of testosterone replacement therapy for hypogonadal men (2). Clearly, this suggests its use in a post-cycle-therapy (as well as its previously discussed use within a cycle) to regain natural testosterone levels and full functioning of the HPTA (Hypothalamic-Testicular-Pituitary-Axis).
Literature provided by the original maker of Anastrozole (Arimidex, produced by Zeneca Pharmaceuticals) states that stable blood plasma concentrations of the compound are achieved after a mere 7 consecutive 1mg daily doses. Also, Arimidex is just over 80% effective at inhibiting aromatase (3). Thus, if you want to take it for the entire duration of a cycle of anabolic steroids, you can simply start taking it on the same day you begin your cycle. Those are some pretty good numbers, huh?
But can you use it for the entire duration of a cycle? Is it dangerous? Well, certainly reducing estrogen levels in your body is good from a body building point of view, as it reduces water-retention and the potential for gynocomastia (if there´s no estrogen in your body, you can´t get gyno, regardless of how much progesterone is floating around)(5). Luckily this stuff is very mild on blood lipids (cholesterol) and doesn´t affect them adversely (2), in the studies I´ve seen.
Arimidex and Cholestrol

As previously mentioned, those lowered estrogen levels could possibly (eventually) adversely affect your cholesterol and possibly even your immune function. I am, however, very comfortable recommending Arimidex for relatively long-term use. This should be the ancillary compound of choice for those on long and heavy cycles, especially since it also doesn´t inhibit igf like some other ancillary compounds (insulin-like-growth-factor is an important component of anabolism)(4).
Price of Arimidex

Though price of Arimidex will vary, this is one of the compounds I will caution the reader from buying in its legitimate pharmaceutical form. The price (up to $5/tab) is absurd, when you consider its availability from Underground Labs, as well as in research form, for less than 1/3rd of that. I´ve used both the tabs from an Underground Lab, as well as the liquid version from research-sites, and found the results from both to be exactly the same.
References:

1. J Clin Endocrinol Metab 2000 Jul;85(7):2370-7, "Estrogen Suppression in Males"
2. Clin Endocrinol (Oxf). 2005 Feb;62(2):228-35.
3. Arimidex Package insert
4. J Steroid Biochem Mol Biol. 2002 Apr;80(4-5):411-8.
5. Progesterone is not essential to the differentiative potential of mammary epithelium in the male mouse. Freeman, Topper. Endocrinology. 1978 Jul;103(1):186-92