Read up on both because there are two camps and little middle ground. Some love arimidex and some love aromasin. There is a ton of information available leaning towards one or the other. When I was taking 200mg a week when I first started TRT, I took arimidex (generic version) and it worked very fast. .5mg the day after injection and on one lab e2 went from 90 to 31 in a day. I have no idea if it creeped back up because I would feel decent until my next shot from an estrogen standpoint.
Here is a lazy cut and paste for an idea:
Arimidex (Anastrozole) is what we call an aromatase inhibitor (AI). In clinical use, it***8217;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***8217;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.
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***8217;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***8217;s no estrogen in your body, you can***8217;t get gyno, regardless of how much progesterone is floating around)(5). Luckily this stuff is very mild on blood lipids (cholesterol) and doesn***8217;t affect them adversely (2), in the studies I***8217;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***8217;t inhibit igf like some other ancillary compounds (insulin-like-growth-factor is an important component of anabolism)(4).
Aromasin (Exemestane) is a steroidal suicide aromatase inhibitor, which means that it lowers estrogen production in the body by blocking the aromatase enzyme, the enzyme responsible for estrogen systemization. (1)(2)(3)
This stuff was developed to fight breast cancer in post-menopausal women, who need a particularly aggressive therapy, and for whom first line defenses such as SERMS (Tamoxifen) have not worked. This should be our first clue in inferring that this stuff is pretty strong, or at least stronger than some of the other compounds which are used to fight breast cancer.
Aromasin and Side Effects
Aromasin averages an 85% rate of estrogen suppression (4), so it***8217;s clearly a very effective agent for bodybuilders and other athletes wanting to avoid estrogen related side effects such as gyno, acne, or water-retention brought on by aromatizing steroids. Specifically, Exemestane dose this by selectively inhibiting aromatase activity in a time-dependent and irreversible manner (hence the "suicidal" portion of it***8217;s name, I guess).(7)
As with most of the compounds in this class, it also causes a reasonable rise in testosterone levels (6), and as you may have guessed, this rise in testosterone means that Exemestane can also cause androgenic sides(8)(9)(10). Exemestane is very effective at both lowering estrogen (estradiol) and raising testosterone:
Estrogen and androgen plasma levels after 10 d of daily exemestane (25 or 50 mg) in healthy young males (mean ± SD; n = 9-11). To convert to System International units: estradiol, Pico moles per liter (x3.671); estrone, picomoles per liter (x3.699); androstenedione, nanomoles per liter (*0.003492); and testosterone, nanomoles per liter (x0.03467). (13)
So we can see that 25mgs is a very effective dose from that chart, right? As an added benefit, exemestane not only increases testosterone and lowers estrogen, but it also increases IGF levels (11).Additionally Worth noting is that Aromasin may possibly be less harsh on blood lipids (14)than some of the other (similar) compounds we use in the world of bodybuilding or athletics (other AI´s). It also has, at best no effect on IGF, and at worst could lower (13) it. AI´s are very tricky with regards to inconsistencies in IGF levels.
Unfortunately, you need to take Exemestane for a week to reach steady blood plasma levels of it, and exemestane has a ½ life of 27 hours (12.).
The ability of exemestane to lower estrogen levels by the aforementioned 85% makes it a very nice choice for use in any cycle where aromatizing steroids are used. In addition, since it***8217;s not too harsh at all on blood lipid profiles, it***8217;s a very good choice for longer cycles. It***8217;s ability to raise both testosterone levels also seem to suggest that it would be a very nice addition to a Post-Cycle-Therapy (PCT).
What about estrogen rebound with Anastrozole? I heard something about it, but can't remember what causes it. Supposedly Aromasin didn't cause this.
By the way, just something interesting: when I first took Anastrozole I took too much at once. It absolutely took away any emotion I had, leaving me like a robot. Which was pretty bad at the time, because I was attending a good friend's funeral and felt zero sadness. It lasted for about a week, weirdest feeling ever! Once it wore off I was able to mourn, and it hit me like a f---in ton of bricks.
I think the rebound discussion is overrated. Unless you are severely prone to e2 sides, I don't see it being an issue. The thing with aromasin is that it is very strong and guys I know that take it and like it, took awhile to get the protocol right because like you, they crushed their e2 for weeks trying to get it right. Plus, it takes 7-10 days to get level in your body. Arimidex works fast and I found that I only had to take it right after injection.
Then again, there are so many pluses for aromasin as well. It supposed to increase IGF, be much less harsh on lipids, and generally well tolerated for long term use once the dose is dialed in.
Pick your poison. Personally, for a little blast, I'd go with a generic arimidex and then once I fell back to TRT doses, stop an AI altogether.