Anastrozole (also known as armidex) is a non-steroidal aromatase inhibiting drug (acronym AI) developed in 1995 by Zeneca Pharmaceucitals for treatment of breast cancer after surgery and for metastasis in women. Anastrozole is used to inhibit the synthesis of estrogen.

Anastrozole use in bodybuilding. When male athletes use anabolic steroids, some of them convert by the aromatase enzyme into the female hormone estradiol (aromatization). The most aromatizing steroids are testosterone esters and methandienone. If estradiol is not inhibited by taking aromatase inhibitors (AI), unpleasant side effects may occur. The most common of them is gynecomastia, i.e. the build-up of female breast tissue in men under impact of female hormone estradiol. Estradiol also causes water retention and increase in the amount of subcutaneous fat. As a result, you can get a rise in blood pressure, heart strain and depression. High levels of estradiol may adversely affect libido.