Anastrozole (Arimidex)

What is anastrozole?

Anastrozole, better known by its trade name Arimidex, is an estrogen blocker that is capable of reducing circulating estrogen levels significantly, by virtue of it being an aromatase inhibitor. Whereas Tamoxifen and Clomiphene only act to block the estrogen receptors, Anastrozole prevents the synthesis of estrogen in the first place, by preventing testosterone’s conversion to it.

Who uses anastrozole?

Anastrozole is an important add on to the cycle of many bodybuilders using aromatizable steroids (such as testosterone and dianabol), or to those individuals especially predisposed and sensitive to the effects of estrogen on the body (endomorphs and individuals with possible teenaged gynaecomastia). Thanks to the long half life of the drug in the body, it is not mandated that you take daily doses; in fact a single 1mg tablet should be able to last 3 days before needing a second dose. If you are concerned about side effects, 0.5mg per day will also work.

When Should Anastrozole Be Used?

Generally, it takes a week for the medication to take full effect, so remembering this detail, if you know that you are likely to develop symptoms, it would be reasonable to take preventive measures. Interestingly, anastrozole can be used while on-cycle, or as part of PCT, although the SERMs (Tamoxifen and Clomiphene) are likely to do a better job there. Estrogen plays a role in stimulating the production of luteinizing hormone (LH), which in turn stimulates the production of testosterone. They may also help to correct blood lipid levels after a cycle, something that anastrozole does not do.

Is anastrozole safe?

For the most part, yes, although there are side effects that some persons may be more prone to develop. For example, liver enzymes may become elevated due to use of it, so persons using other liver toxic drugs need to keep that in mind. Secondly, the risk of bone fractures increases somewhat since the protective role of estrogen is no longer there. A phenomenon known as “shin splints” may occur frequently. Anastrozole should not be used by women unless under the guidance of a physician. There have been reports of fetal abnormalities occurring following its use.


  • Anastrozole has been used as a standalone drug by “natural athletes” as a testosterone booster. It is purported to raise testosterone levels up to 58%.
  • Anastrozole should not be taken by pre-menopausal women as it may accelerate osteoporosis and premature menopause.
  • Joint pain and cracking commonly occur with the use of this medication.
  • Anastrozole can easily increase the cost of your cycle if you use the specialty product Arimidex (which can cost up to $10 per tab).