Exemestane(Aromasin) is very similar in structure and action to formestane, although it is significantly more potent in comparison. As a class of drugs, aromatase inhibitors offer an anti-estrogenic effect by blocking the enzyme responsible for synthesizing estrogens. Therefore male bodybuilders and athletes use Aromasin to counter the estrogenic side effects associated with the use of aromatizable anabolic/androgenic steroids.
As an aromatase inhibitor, Aromasin’s mechanism of action — blocking conversion of aromatizable steroids to estrogen — is in contrast to the mechanism of action of anti-estrogens such as Clomiphene (Klomen) or Tamoxifen (Nolvadex, Tadex), which block estrogen receptors in some tissues, and activate estrogen receptors in others. During a cycle, if using Aromasin, there is generally no need to use Klomen as well, but there may still be benefits to doing so.