Arimidex (anastrozole) is the aromatase inhibitor of choice. The drug is appropriately used when using substantial amounts of aromatizing steroids, or when one is prone to gynecomastia and using moderate amounts of such steroids. Arimidex does not have the side effects of aminoglutethimide (Cytadren) and can achieve a high degree of estrogen blockade, much more so than Cytadren. It is possible to reduce estrogen too much with Arimidex, and for these reasons blood tests, or less preferably salivary tests, should be taken after the first week of use to determine if the dosing is correct. As an aromatase inhibitor, Arimidex mechanism of action — blocking conversion of aromatizable steroids to estrogen is in contrast to the mechanism of action of anti-estrogens.