Aromasin (exemestane) is a steroidal suicide aromatase inhibitor. It 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. Aromasin is approved by the FDA for the treatment of breast cancer in women, specifically in post-menopausal patients whose cancer has progressed following therapy with tamoxifen. Male bodybuilders and athletes often use the drug for non-approved purposes, namely to counter the estrogenic side effects associated with the use of aromatizable anabolic/androgenic steroids.