Aromatase inhibitors are the compounds that serve to reduce estradiol levels in blood by eliminating the production of estradiol through binding to and disabling the aromatase enzyme, which is responsible for the conversion (or aromatization) of androgens into estradiol. Suicidal aromatase inhibitors 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 the main difference compared alongside two other major aromatase inhibitors: anastrozole and letrozole, which are non-suicidal aromatase inhibitors that are only bound to the aromatase enzyme for limited time periods. 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 Exos.
Transdermal patches (adhesive patches placed on the skin) may also be used to deliver a steady dose through the skin and into the bloodstream. Testosterone-containing creams and gels that are applied daily to the skin are also available, but absorption is inefficient (roughly 10%, varying between individuals) and these treatments tend to be more expensive. Individuals who are especially physically active and/or bathe often may not be good candidates, since the medication can be washed off and may take up to six hours to be fully absorbed. There is also the risk that an intimate partner or child may come in contact with the application site and inadvertently dose himself or herself; children and women are highly sensitive to testosterone and can suffer unintended masculinization and health effects, even from small doses. Injection is the most common method used by individuals administering AAS for non-medical purposes.