Aromasin is a very strong and very potent steroidal aromatase inhibitor of the suicidal type, and information within the packaging in prescription Aromasin describes the ability for Aromasin to reduce Estrogen levels by 85%, as evidenced by studies on breast cancer patients. Suicidal aromatase inhibitors such as Aromasin (Exemestane) serve to permanently inhibit and disable the aromatase enzyme to which it is bound to. This renders the enzyme inactive forever. The body will eventually manufacture more aromatase enzymes, but the currently bound enzymes are bound indefinitely, eliminating any risk for Estrogen rebound. This is unseen with the other two major aromatase inhibitors ( Arimidex and Letrozole), which are non-suicidal aromatase inhibitors that are only bound to the aromatase enzyme for limited time periods before the aromatase inhibitors unbind and become metabolized. If a non-suicidal aromatase inhibitor is halted too abruptly, the circulating inhibited aromatase enzymes that have not been metabolized out of the body will then become free again, and begin aromatizing androgens into Estrogens at an often-rapid rate. This is not the case with Aromasin.