Arimmidex

Chemical Name: Anastrozole 
Drug Class: Type II Aromatase Inhibitor

Arimidex is a type-II aromatase inhibitor (called an AI). In the case of Arimidex, or any Type-I inhibitor, it works by binding to the substrate (the aromatase enzyme) thus rendering it inactive and therefore unable to convert testosterone into estrogen. Drugs in this class are used to halt the progression of Breast Cancer in women, as well as for a preventative measure in women who are high risk. In bodybuilding, it is used as an ancillary compound on a cycle containing steroids which aromatize into estrogen.

The primary reason we would use something like this is because excess estrogen in males can have many undesirable effects such as causing a more “watery looking” weight gain, or even development of breast tissue in males.

Arimidex stops or slows the conversion of testosterone into estrogen, and thus helps to prevent those side effects from occurring. Typically, in breast cancer studies, we see a dose of about 1mg/day being used, and in steroid using athletes, this is also the amount we would often see. That dose may be slightly excessive, however. In a study conducted on males, examining estrogen suppression in males caused by Arimidex, both .5mg and 1mg doses of were shown to decrease estrogen by around 50%. In both the 1 and .5mg groups in that same study, testosterone levels were raised significantly and both LH and FSH also went up slightly. (1)

In my mind, this is reason enough to suggest only using the stuff at a dose of .5mgs/day, as a preventative measure against water retention and gyno. If, however, you are trying to actually reduce pain from breast tissue which has already begun to hurt and show early signs of gyno, then you’ll have to use the full 1mg dose, even though it only provides a slight % more estrogen suppression.

Also for pricing reasons, instead of gaining a few % you could save a lot of money by simply halving the dosage amount.

When testosterone converts to estrogen in males, it feeds into the negative feedback loop that causes testosterone to cease being produced. Therefore, most compounds that will lower aromatization, such as an AI like Arimidex, will also raise testosterone by inhibition of the negative feedback loop that signals your body to halt testosterone production. In fact, in the case of Arimidex, the elevation in Testosterone provided by the inhibition of estrogen is so large that it can actually be used as a very mild form of testosterone replacement therapy for already hypogonadal men (2). This then does seem to make it very good for a post cycle routine but I would keep it on a cycle as the raised testosterone is a benefit and there are better for a post cycle.

Blood plasma concentrations become stable by 7 consecutive 1mg daily doses, although maximal estrogen inhibition is reached by day 4. (3) Arimidex is over 80% effective at inhibiting the aromatase enzyme (3) and if you are considering using it for the entire duration of your cycle, then you don’t have to “front load” or even start it before the cycle as some have suggested. Simply start taking it on Day one of the cycle. Since the average cycle seems to fall around 12 weeks, Arimidex is actually a very nice choice for use during the entire duration of the cycle, because it’s got the advantage of not affect cholesterol adversely (2).

References:

1. J Clin Endocrinol Metab 2000 Jul;85(7):2370-7, " Estrogen Suppression in Males"

2. Clin Endocrinol (Oxf). 2005 Feb;62(2):228-35.

3. From  Arimidex Package insert, Astra Zeneca Pharmaceuticals.