Active: Letrozole/Anastrozole

Overview and History of Arimidex

Arimidex belongs to a category and class of drugs known as aromatase inhibitors (AIs). Aromatase inhibitors belong to an even broader class of drugs known as anti-estrogens. The other subcategory of drugs under the anti-estrogens category is known as selective estrogen receptor modulators (SERMs), such as Nolvadex and Clomid. AIs and SERMs make up anti-estrogens. Aromatase inhibitors differ greatly from SERMs in their actions and how they deal with the issues of estrogen control. The misunderstanding that SERMs, such as Nolvadex and Clomid, serve to lower estrogen levels must first be addressed.

This is a persistent rumor among the bodybuilding community that has begun to erode as of late. SERMs serve to block the action of Estrogen at the receptor sites in breast tissue. Estrogen, therefore, cannot exert its effects there through the receptor. SERMs will also act as Estrogens at receptor sites in other cells throughout the body, liver, for example. SERMs do not lower circulating levels of Estrogen in blood plasma. Aromatase inhibitors do this by eliminating the production of Estrogen. It disables the aromatase enzyme responsible for the estrogen conversion (or aromatization) of androgens into Estrogen.


Zeneca Pharmaceuticals (now AstraZeneca) developed Arimidex as an aromatase inhibitor. synthesized and designed to treat female patients suffering from advanced breast cancer. FDA approval came in 1995 and they released it onto the American prescription drug market. Arimidex is as viewed as one of the newer aromatase inhibitors, known as a third-generation aromatase inhibitor. The reason why both aromatase inhibitors and SERMs act to block Estrogen’s effects in different ways. They found that estrogen stimulates and accelerates the majority of breast cancers.

Arimidex is used among breast cancer treatments as an adjunct treatment. This refers to an additional treatment when other standard treatments have failed to meet proper expectations. Before the development and release of Arimidex as a breast cancer treatment medication, the primary medication used for treatment for decades prior was Nolvadex (Tamoxifen). Nolvadex is the standard treatment for breast cancer patients. When Nolvadex treatment cannot meet expectations during breast cancer treatment, second-line adjunct drugs such as Arimidex are used.

Further Studies

They did one such study on Arimidex with over 9,000 post-surgery female breast cancer patients. It observed its efficiency compared to Nolvadex (both alone and both together), resulting in far more favorable outcomes for Arimidex over Nolvadex. The study in 2002 concluded that Arimidex was far more effective at cancer regression. Increasing the survival rate of breast cancer patients following treatment. It was then this study (and others) prompted interest among the anabolic steroid community. They began investigating the benefits of its effects on strong Estrogen levels suppression.

A later study showed the risk of recurrence of breast cancer reduced by 40% with Arimidex use. However, patients experienced an increase in bone fractures. Maintenance of proper mineral retention reduces because of low estrogen levels caused by Arimidex use.

A first for bodybuilders

Because Arimidex was the very first aromatase inhibitor for many bodybuilders to have taken notice of, it is the most popular aromatase inhibitor used among anabolic steroid users for Estrogen control. Used with anabolic steroids by athletes for the control of almost all Estrogen-related side effects such as gynecomastia, water retention and bloating, rising blood pressure (because of water retention increases from Estrogen).

This is in contrast with SERMs such as Nolvadex, which only block gynecomastia. Studies have shown that Arimidex use in males has is very effective. Reduction of circulating Estrogen blood plasma levels by as much as 50% at only a dose of 0.5 – 1mg daily. This is a considerable decrease in men.  It is still much lower than the 80% reduction observed in female breast cancer patients. However, there are significant differences between the sexes.

Aside from the use in bodybuilders, Arimidex has also had uses in males. Males who exhibit high levels of Estrogen use Arimidex to combat these ailments. Arimidex has been used to treat male adolescents that exhibit excessive Estrogen levels during puberty, resulting in unwanted pubertal gynecomastia. Excessive Estrogen levels in adolescent males can cause stunted growth. This is because Estrogen plays a key role in fusing the growth plates of the bones shut, preventing any further linear growth.

Chemical Characteristics of Arimidex

Arimidex is a non-steroidal aromatase inhibitor. This is to say that it does not possess the characteristic four ring cycloalkane ring carbon structure common of all types of steroids.

Properties of Arimidex

Arimidex’s effects on serum Estrogen level control can be quite drastic even at a dose of 1mg daily. Over 80% of patients showed estrogen reduction. Arimidex can be so effective at inhibiting the aromatase enzyme and thereby reducing Estrogen levels that this compound is typically only administered to post-menopausal females, and/or utilized when other first-line treatments for breast cancer has failed.

Arimidex and Letrozole are both classified as non-steroidal and non-suicidal aromatase inhibitors. They both compete with the substrate for binding to the enzyme active site. This is very different from Aromasin (Exemestane). A sterodial and suicidal aromatase inhibitor that acts as a mechanism-based steroidal inhibitor. It mimics the substrate and is converted by the enzyme to a reactive intermediate. This deactivates the aromatase enzyme.

Aromasin’s chemical structure resembles the traditional points that bind to Testosterone. It essentially ‘fools’ the aromatase enzyme into binding with it, only to become inhibited/deactivated. Because the binding strength is so great, this inhibition becomes permanent for the aromatase enzyme. Arimidex and Letrozole, being non-suicidal aromatase inhibitors, both compete with the enzyme’s traditional ‘targets’ rather than being assured a permanent spot (which is the advantage that Aromasin has over the other two).

Bodybuilders and athletes utilizing anabolic steroids will usually favor aromatase inhibitors such as Arimidex for its ability to eliminate rising Estrogen levels at its root cause: aromatase. By disabling the aromatase enzyme, levels of androgens that can aromatise (such as Testosterone, Dianabol, etc.) cannot convert into Estrogen, thereby eliminating any possible risk of Estrogen-related side effects.

Arimidex Side Effects

Arimidex (Anastrozole) is an ancillary compound for Estrogen control in the body. Male users generally tolerate it well. There are, however, some Arimidex side effects that cause concerned. This primarily exists in the form of excess reduction of blood plasma levels of Estrogen in the body, as well as long-term Estrogen suppression. Arimidex does affect females in a far greater and significant manner than it does in male users as well.

When it comes to Estrogen reduction and suppression, it must be understood that unlike SERMs (Selective Estrogen Receptor Modulators) such as Nolvadex or Clomid (Clomiphene Citrate), Arimidex belongs to the family of aromatase inhibitors. This means that it serves to disable the aromatase enzyme, which is responsible for the aromatization – or, conversion – of Testosterone into Estrogen. In other words, Arimidex reduces total circulating Estrogen levels at the root source as opposed to SERMs, which serve to merely block the activity of Estrogen at select receptor sites.

Studies have demonstrated that Arimidex use results in the increased incidence and probability of experiencing bone fractures. Although this is a more female-specific side effect of Arimidex use, Estrogen does play an important role in the promotion and retention of bone mineral content in males as well. Studies conducted discovered that Arimidex negatively impacts calcium turnover levels in bone tissue. Even with short term use.

Most Common Side Effects

We commonly associate lethargy and fatigue with Arimidex use. As with nearly all Estrogen reduction compounds, a reduction in circulating Estrogen levels means that the important role that Estrogen plays in the CNS (Central Nervous System) is reduced, thus resulting in possible instances of chronic fatigue. This results from Estrogen levels being reduced. These levels are far too low to be healthy.

One particularly prominent side effect of Arimidex use is the negative impact on blood cholesterol profiles. As with nearly all Estrogen reducing compounds, Arimidex will also decrease HDL (good) cholesterol and increase LDL (bad cholesterol). This is because Estrogen is responsible for the promotion of healthy cholesterol levels in the body. Disruption of normal blood plasma levels of Estrogen will indeed throw that off. The more severe the reduction of Estrogen, the more severe the cardiovascular impacts.

The possibility of an Estrogen rebound is an important sided effect. This exists in particular with two of the three most popular aromatase inhibitors (Arimidex and Letrozole). The third aromatase inhibitor, Aromasin (Exemestane) does not share this same attribute of the possibility of Estrogen rebound. This is because unlike Aromasin, Arimidex is a non-suicidal aromatase inhibitor. This means that Arimidex will bind with and disable the aromatase enzyme, but it does not do it permanently. At some point, Arimidex will dissociate with the enzyme and the enzyme will then be free to do its job again in the body. This means there is the risk of Estrogen levels rebounding (and thus, Estrogen related side effects) if you halt Arimidex use to soon.

Dosing and Administration of Arimidex

Arimidex (Anastrozole) treats post-menopausal female breast cancer where the primary cause is Estrogen. The dosage of Arimidex in these cases call for 1mg taken once per day until the progression of cancer has stopped.

Arimidex For Gynecomastia and Estrogen Control On-Cycle

Use 0.5 – 1mg per day for control of Gynecomastia and Estrogen while on a cycle. The user can adjust this depending on tolerance and reaction to the compound. Everyone should adjust their Arimidex dosage according to their response. It is not uncommon for 0.5mg/day to even be too much (or too little) for some. Remember that the purpose here is Estrogen control during a cycle, not total elimination of Estrogen levels.

Arimidex For Post Cycle Therapy (PCT)

Studies have shown that Arimidex can assist in endogenous natural Testosterone production in males. A dosage of 0.5mg to 1mg per day should be sufficient for the duration of any PCT length.

It possesses a half-life of approximately 48 hours. Blood plasma level peak only after 7 days of consistent use. You can take it at any time of day, with or without food.

Estrogen Elimination Dangers

Attempt to avoid the use of aromatase inhibitors at all costs unless necessary. If the use of an aromatase inhibitor is necessary, utilize it only when required. Attempt the lowest possible dose for Estrogen control rather than Estrogen elimination.

It is of importance to readers investigating aromatize inhibitors. The use of aromatase inhibitors, like the three primary AIs (Arimidex, Aromasin, and Letrozole), have serious negative effects on the body. Especially when used when not needed, or used too often.

The reason for the use of an aromatase inhibitor should always be for Estrogen control rather than elimination. The complete and total reduction of all Estrogen levels in the body results in serious effects in the human body.

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