Exemestane Powder in comparisson to other anti estrogens is a steroid, it is very similiar to the chemical structure of foremestane, but also much more effective. It is an extremely potent drug which is responsible for entirely blocking any estrogen production. This is to be used very carefully when it is being used without a medical prescription. In comparisson to arimidex which possess a reversible effect, exemestane possesses an ihibitor effect of aromataze steroid which is irreversible, meaning that when they bind together they do not metabolize into aromataze which stops the aromatization of estrogen from androgens.