Anastrozole is an extremely powerful anti-estrogen officially belonging to the Aromatase Inhibitor (AI) family. Developed in the early 1990’s by Zenaca Pharmaceuticals and released in 1995 under the trade name Arimidex, this is perhaps the most commonly used AI and one of the most common anti-estrogens on the market.

Anastrozole belongs to a new generation of nonsteroidal aromatase inhibitors used in disseminated breast cancer in postmenopausal women. Anastrozole inhibited estrogen-dependent reproduction and growth of breast cells. The mechanism of action of anastrozole is associated with selective inhibition of aromatase, an enzyme of the cytochrome P450 system. The main source of circulating estrogen in postmenopausal women are androgens, primarily androstenedione and testosterone. Aromatase provides their multiple hydroxylation with transformation into estrone, and then into estradiol in adipose and muscle tissue, liver, adrenal glands and in tumor tissue.

Anastrozole use in bodybuilding when male athletes use anabolic steroids, some of them convert by the aromatase enzyme into the female hormone estradiol (aromatization). If estradiol is not inhibited by taking aromatase inhibitors (AI), unpleasant side effects may occur.