Anastrozole (AKA Arimidex)

Overview and History of Arimidex

Arimidex belongs to a category and class of medications known as aromatase inhibitors (AIs).

Aromatase inhibitors belong to a much broader class of medications known as anti-estrogens.

Another subcategory of drugs in the anti-estrogen category is known as selective estrogen receptor modulators (SERMs), such as Nolvadex and Clomid.

Aromatase inhibitors and SERMs make up the class of anti-estrogens.

Aromatase inhibitors differ significantly from SERMs in how they work and how they address estrogen regulation.

It's important to clear up the misconception that SERMs like Nolvadex and Clomid act to lower estrogen levels.

This is a myth that has only recently begun to die down in the anabolic steroid-using community, but it still persists.

SERMs act to block estrogen's receptor site action by taking the place of estrogen, preventing estrogen itself from exerting its effects in breast tissue through receptor site binding.

Conversely, SERMs also act as estrogen at the receptor site on other cells in other parts of the body (e.g., the liver in the case of Nolvadex).

SERMs do not lower circulating levels of estrogen in the plasma.

Aromatase inhibitors do this by eliminating estrogen production by binding to and neutralizing the aromatase enzyme, the enzyme that converts (or aromatizes) androgens into estrogen.

Arimidex was originally synthesized and designed as an aromatase inhibitor developed by Genentech Pharmaceuticals (now AstraZeneca) for the treatment of female patients with advanced breast cancer.

It was approved for use by the FDA and introduced to the U.S. prescription drug market in 1995.

Arimidex is considered one of the newest aromatase inhibitors, known as a third-generation aromatase inhibitor[1].

The reason aromatase inhibitors and SERMs block the effects of estrogen in different ways is because it has been found that most breast cancers are stimulated and promoted by estrogen.

Arimidex is known as an adjuvant treatment during breast cancer treatment.

This is typically an additional treatment used when other standard treatments have not met appropriate expectations.

Before Arimidex was developed and launched as a treatment for breast cancer, the drug that had been used for decades to treat the disease was Nolvadex (tamoxifen).

Nolvadex is known to be utilized as a first-line and standard treatment for breast cancer patients.

During breast cancer treatment, if Nolvadex treatment does not meet expectations for various reasons, second-line adjuvant drugs such as Arimidex are used.

In one study of Arimidex involving over 9,000 post-operative female breast cancer patients, it was observed that compared to Nolvadex (both alone and in combination), Arimidex had significantly more favorable outcomes than Nolvadex [2].

This study, conducted in 2002, concluded that Arimidex was significantly more effective in regressing cancer and also increased the survival rate of breast cancer patients after treatment [3].

With this and other studies, it was only natural for the anabolic steroid-using community to take notice of Arimidex and begin researching its potent estrogen suppression effects.

Subsequent studies have shown that while Arimidex use reduced the risk of breast cancer recurrence by 40%, patients experienced an increase in fractures[4].

This is because estrogen plays a key role in the proper maintenance of bone and mineral retention, which is significantly reduced by the significant decrease in estrogen levels caused by Arimidex administration.

Arimidex is the most commonly used aromatase inhibitor among anabolic steroid users for the purpose of estrogen control, as it was the first aromatase inhibitor to come to the attention of many bodybuilders.

It is used to control almost all estrogen-related side effects among athletes using anabolic steroids, namely gynecomastia, water retention and bloating, and increased blood pressure (a result of estrogen-induced increased water retention).

This is in contrast to SERMs like Nolvadex, which only act to block gynecomastia.

In fact, studies have shown that using Arimidex in men is effective enough to reduce blood estrogen levels by 50% with a daily dose of just 0.5 to 1 mg [5].

While this is a very significant reduction in men, and quite different from the 80% reduction in female breast cancer patients, it is important to remember that estrogen and women's physiology are different than men's.

In addition to its use in bodybuilders, Arimidex has also been used medicinally in men [6].

Some men have abnormally high estrogen levels for a variety of reasons, and Arimidex has been utilized to treat these conditions.

In particular, Arimidex has been used to treat male adolescents who exhibit excessive estrogen levels during puberty, causing unwanted pubertal gynecomastia [7] [8].

Excessive estrogen levels in male adolescents during puberty can also often result in stunted growth, as estrogen plays an important role in fusing the growth plates of bones, preventing further linear growth, and Arimidex has also been used to treat this condition [9] [10].

Chemical Properties of Arimidex

Arimidex is a non-steroidal aromatase inhibitor.

This means that it does not have the characteristic 4-membered cycloalkane ring carbon structure common to all types of steroids.

Characteristics of Arimidex

The effectiveness of Arimidex in controlling serum estrogen levels is quite significant at a dose of 1 mg daily.

Estrogen suppression at this dose has been demonstrated in over 80% of patients.

Because Arimidex is so effective at lowering estrogen levels by inhibiting the aromatase enzyme, it is typically only given to postmenopausal women or when other first-line treatments for breast cancer have failed.

Both Arimidex and letrozole are classified as non-steroidal and non-lethal aromatase inhibitors, which compete with substrates for binding to the enzyme's active site.

This is very different from aromasin (Exemestane), which is a steroidal and suicidal aromatase inhibitor based on a mechanism that mimics the substrate and is converted by the enzyme into a reactive intermediate, resulting in the inactivation of the aromatase enzyme.

In layman's terms, this means that aromasin's chemical structure is similar to the traditional 'targets' that aromatase binds to (e.g. testosterone), and it essentially 'tricks' the aromatase enzyme into binding to inhibit/inactivate it.

Because the binding strength is so strong, this inhibition of the aromatase enzyme that aromasin binds to is permanent.

Since Arimidex and Letrozole are non-lethal aromatase inhibitors, they compete with the traditional 'target' of the enzyme instead of securing a permanent spot (an advantage of aromasin over the other two).

Bodybuilders and athletes who use anabolic steroids prefer aromatase inhibitors like Arimidex because of their ability to eliminate aromatase, which is the root cause of elevated estrogen levels.

By neutralizing the aromatase enzyme, supraphysiological levels of aromatizable androgens such as testosterone, dianabol, and boldenone are not converted to estrogen, eliminating the risk of estrogen-related side effects.

Arimidex Side Effects

Arimidex (Anastrozole) is a compound that is generally well tolerated by male users because it is a secondary compound that aims to regulate estrogen in the body.

However, there are a few Arimidex side effects to be concerned about.

These mainly come in the form of excessive decrease in plasma levels of estrogen in the body and long-term estrogen suppression.

Arimidex affects women in a much greater and more significant way than male users.

When it comes to estrogen reduction and suppression, it's important to understand that unlike SERMs (selective estrogen receptor modulators) like Nolvadex or Clomid (clomiphene citrate), Arimidex belongs to the aromatase inhibitor family.

This means that it works by neutralizing the aromatase enzyme, which is responsible for the aromatization or conversion of testosterone into estrogen.

In other words, unlike SERMs, which work to block the activity of estrogen at specific receptor sites, Arimidex reduces total circulating estrogen levels at the root cause.

Studies have demonstrated that the use of Arimidex increases the incidence and probability of fractures.

While this is a female-specific side effect of Arimidex use, estrogen also plays an important role in promoting and maintaining bone density in men.

Studies have shown that even short-term use of Arimidex negatively affects calcium turnover in bone tissue.

Lethargy and fatigue are commonly associated with Arimidex use.

As with almost all estrogen reducing compounds, a decrease in circulating estrogen levels can lead to chronic fatigue due to a decrease in the important role estrogen plays in the central nervous system.

This is usually the result of estrogen levels being lowered to unhealthy levels.

One particularly prominent side effect of Arimidex use is its negative impact on blood cholesterol levels.

Like almost all estrogen-reducing compounds, Arimidex decreases HDL (good) cholesterol and increases LDL (bad) cholesterol.

This is because estrogen is responsible for promoting healthy cholesterol levels in the body, and this action is disrupted when plasma levels of estrogen are not maintained.

Of course, it goes without saying that the more severe the decrease in estrogen, the more severe the effects on the cardiovascular system.

One of the important side effects of Arimidex is the possibility of estrogen rebound.

This is particularly present with two of the three most commonly used aromatase inhibitors (Arimidex and Letrozole).

The third aromatase inhibitor, aromasin (Exemestane), does not share the same property of estrogen rebound potential.

This is because, unlike aromasin, Arimidex is a non-lethal aromatase inhibitor.

That is, Arimidex binds to and neutralizes the aromatase enzyme, but does not act permanently.

At some point, Arimidex will dissociate from the enzyme and the enzyme will be free to do its job in the body again.

What this means for the end user is that if you stop using Arimidex too soon or abruptly after starting, you run the risk of estrogen levels rebounding (and therefore estrogen-related side effects).

Dosage and administration of Arimidex

Medically, Arimidex (anastrozole) is used to treat breast cancer in postmenopausal women where estrogen has been found to be the primary cause.

In these cases, the prescribed dose and administration of Arimidex is 1 mg once a day until the cancer stops progressing.

Arimidex on cycle for gynecomastia and estrogen control

For gynecomastia control and general on-cycle estrogen control, Arimidex should generally be used in the range of 0.5 to 1 mg per day, which can be adjusted based on the user's tolerance and response to the compound.

Everyone should adjust their Arimidex dosage based on their individual response.

It is not uncommon for 0.5mg per day to be too much or too little for some people.

You should also always remember that the goal here is to regulate estrogen during the cycle, not to completely eliminate estrogen levels.

Arimidex for Post Cycle Therapy (PCT)

Arimidex has been shown in studies to support endogenous natural testosterone production in men, so a dose of 0.5mg to 1mg of Arimidex per day is sufficient during PCT.

It's also important to understand that Arimidex has a half-life of approximately 48 hours, and that peak plasma concentrations can only be reached after a week (7 days) of consistent dosing.

Arimidex can be taken at any time of the day, with or without meals.

Legality and availability of Arimidex

Arimidex is an unregulated substance in most countries around the world.

Most notably, in Canada and the United States, it is a prescription-only product, but as it is not a controlled substance, it can be legally owned, purchased, and possessed, but it is not available over the counter domestically.

In the United Kingdom, the legality of Arimidex is the same.

In many countries in Eastern Europe, Asia, and the Middle East, Arimidex is often available without a prescription.