Thread: Arimidex and Aromasin Explained

Arimidex (Anastrozole) Explained
Arimidex (Anastrozole)

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.

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.

Aromasin (Exemestane) Explained
Aromasin (Exemestane)

Control of estrogen levels is often necessary in anabolic steroids, due to aromatization of steroids such as testosterone, Dianabol, nandrolone (Deca), or boldenone (Equipoise.) In the aromatization process, the aromatase enzyme converts these androgens to estrogen. If this conversion is excessive, bloat, depression, loss of libido, impaired fat loss, or even gynecomastia can occur. An aromatase inhibitor (AI) is an effective way to solve this problem.

In contrast to Arimidex and letrozole which work by reversibly blocking access to the aromatase enzyme, Aromasin actually inactives individual enzyme molecules when it binds to them.

There is really neither advantage nor disadvantage to this different mode of action. As with all aromatase inhibitors, Aromasin should be dosed to achieve optimal estradiol levels, not the lowest possible levels. When dosed correctly and achieving the same estradiol levels, it doesn’t make a difference what inhibition mechanism was used.

How then to choose between aromatase inhibitors?

The relevant factors really are only previous experience if any, availability, cost, convenience, and side effect profile.

Not much distinguishes the aromatase inhibitors from each other in terms of side effect profile. I disfavor Aromasin slightly on this account as there’s some evidence of hepatotoxicity, but this is a rare enough side effect that as a matter of personal choice, factors such as personal experience may outweigh it.

Aromasin is usually supplied in 25 mg tablets. Dosing of Aromasin in anabolic steroid cycles is most commonly 12.5 mg every other day, 12.5 mg daily, or at most 25 mg daily.

Excessive dosing will be recognized by estradiol level falling below 20 pg/mL, or by depression, reduction of libido, muscle flatness, and/or joint pain. Experienced users frequently are able to identify a need for dose reduction purely from symptoms. However, blood testing is the gold standard for determining correct dosing level, and for verifying that symptoms actually are caused by low estrogen.

As with other aromatase inhibitors, there’s a relation between the amount of aromatizable steroids used and the dose of inhibitor needed, but it’s not a purely proportional matter. For example, let’s say that a previous cycle a lifter used 250 mg/week of testosterone, along with 750 mg/week of non-aromatizable steroids. And let’s say he found 12.5 mg/day Aromasin to be suitable for that cycle. If he now wishes to use 1000 mg/week of testosterone, which is four times more, most likely he should not multiply his Aromasin dosage by four times. That would be 50 mg/day which is outside of the normal dosage range. I would recommend 25 mg/day as an estimated dose in this instance.

I have never derived exact formulas for adjustment of dose according to change in amount of aromatizable steroids. Most likely there really is no universal formula. As general advice however, make a reasonable estimate which provides some increase to account for increased amount of aromatizable steroids, but without exceeding the recommended range unless blood testing proves that necessary.
Some use Aromasin during PCT, but I’d do this only if blood testing shows elevated estradiol levels. If that’s the case, then Aromasin is to a small extent actually the preferred aromatase inhibitor over Arimidex or letrozole in this instance, because the other two may have some interaction with the metabolism of SERMs, while Aromasin does not.

If used in PCT, dosing should be markedly less than during a cycle, as amount of aromatizable steroid in the blood will be much less. Generally no more than 12.5 mg every other day will be needed, or even only every third or fourth day.

Although mentioned already above, as a closing point I’d like to re-iterate that there really is no issue of the relative strength of differing aromatase inhibitors, and no reason to chose one over another on account of claimed strength differences. Let’s say that a dosing of one aromatase inibitor is stronger – reduces estrogen more – than a dosing of another. If the first one reduced estrogen too much, then the dosing was too many milligrams. It’s not the product was “too strong.” Or, if the second one didn’t reduce estradiol enough, then the dosing was too few milligrams, rather than the product not being strong enough.

All of the aromatase inhibitors will overshoot estrogen reduction if overdosed, or undershoot if underdosed. There is no reason to choose one over another because of what any may say about strength.

Arimidex, letrozole, and Aromasin all are capable of working well and predictably for estrogen control. If already experienced with a given aromatase inhibitor, I recommend continuing with it, as personal dosing is already understood. If you have not yet tried any, then any of them can be effective. I hope the above explanation will assist you in your choice.


I am a part time Proctologist and full time Gynecologist

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