Arimidex (anastrozole)

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Arimidex (anastrozole) was the first selective aromatase inhibitor used in bodybuilding, and is still the most popular estrogen control drug. It’s commonly available in both tablet and liquid form for oral use. Dosing is typically 0.25, 0.5, or 1.0 mg at a time, at a frequency of once per day or per two days.

Estradiol, the most potent form of estrogen, is produced in the body by aromatization of testosterone. This occurs via the aromatase enzyme. Because certain levels of estradiol are needed for men, some conversion of testosterone to estradiol is required. However, in two circumstances effective aromatase inhibition can give important benefits.

First, when an anabolic steroid cycle causes very aromatizable steroid levels and there is no control of the aromatase enzyme, conversion to estradiol becomes excessive. The resulting high estradiol can cause gynecomastia, water retention, depression, and/or loss of libido. It may also make it difficult to maintain a lean condition.

And second, some men have excessive estradiol levels even when not on an anabolic steroid cycle. This will act to decrease their natural testosterone production, and can also cause the above adverse side effects.

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Arimidex is highly suitable for solving either problem. With correctly chosen dosing, free estradiol level can be brought fairly accurately to a desired range. When not using anabolic steroids, for most men I recommend about 20-29 pg/mL for best effect on mood, performance, libido, and long term health and to provide excellent benefit to natural testosterone production. During a steroid cycle, levels can be allowed to rise a little higher, because high androgen levels act towards countering adverse actions of estradiol. Sometimes levels are deliberately made higher, as being a little “wet” can improve lifting performance. Still, I recommend that even during a strong anabolic cycle, estradiol level be kept to no more than about 40 pg/mL.This will usually require an aromatase inhibitor such as Arimidex, if dosing of aromatizable steroids is high.

The most highly aromatizing steroids are testosterone, methyltestosterone, and Dianabol, but Deca (nandrolone) and Equipoise (boldenone) also aromatize.

Most medical studies of effect of Arimidex on men have used it at 1 mg/day, with this dosage appearing about optimal judging from effect on estradiol level. However, real world use for either steroid cycles or optimization of hormone levels is generally at a lower dosage, from 0.25 mg every other day to about 0.5 mg/day. I generally recommend 0.5 mg every other day as a starting point for a steroid cycle, and half that for hormone optimization if a high estrogen problem exists.

Overdosing of Arimidex leads to abnormally low estradiol level and typical side effects of joint pain, reduced libido, and/or gastrointestinal distress. The first two are directly caused by low estradiol. If experiencing these effects, reduce dose. Effect on the GI tract appears a side effect of Arimidex itself, but one which fortunately affects only a few. If experiencing this effect, I recommend switching to letrozole as an alternate choice of aromatase inibitor.

Anastrozole has a half life of about two days. For this reason, when use is ongoing, on taking a dose of Arimidex the user will have in his system not only the dose that he just took, but also about another two days’ worth that has built up in his system. If just starting usage, however, there is no such buildup and effect will be less.

Rather than waiting a couple of weeks for buildup to occur, I instead recommend frontloading Arimidex. This is done by taking as the first dose not only the regular amount, but also an additional two days’ worth. For example, if intending to take 0.5 mg every other day, then this would be an additional 0.5 mg. The frontloading dose would therefore be 1.0 mg. This would be taken only on the first day of use. With this method, the proper effect is achieved nearly immediately.

A controversial use of Arimidex is in PCT. Some advocate driving estradiol levels abnormally low in PCT in order to stimulate testosterone production; I’m a strong advocate of instead using a SERM such as Nolvadex or Clomid instead. However, if a person needs Arimidex even off-cycle due to his having naturally high aromatization, then his off-cycle dosage may be employed during PCT as well.

Arimidex is best compared with letrozole. Either drug can be used effectively for aromatase control. The choice between them can be made entirely on personal preference, experience, and availability.

Bill Roberts
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