Exemestane (also known as Aromasin) is a very strong and potent steroidal aromatase inhibitor (AI) of the suicidal type. Exemestane permanently inhibits and disables the aromatase enzyme to which it is bound; 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 as compared with the two other major aromatase inhibitors, anastrozole and letrozole. 

Exemestane has positive qualities that make it superior in many regards to other types of aromatase inhibitors. Exemestane is a steroidal AI, which keeps it from negatively affecting lipid profiles (cholesterol levels) like some other non-steroidal aromatase inhibitors. Also, it is not liver toxic and can be run for longer lengths of time without negative consequences. This makes exemestane a better option to run during a cycle from a pure health standpoint. Another benefit is that exemestane lowers SHBG significantly, which, as a result, increases the bioavailability of testosterone and cycle efficiency. In addition, exemestane even increases IGF-1 levels. Exemestane is a very powerful and effective treatment for gynecomastia as well, and there is no risk of estrogen rebound when using exemestane because it is a suicide inhibitor (it irreversibly bonds to the target enzyme). When a non-suicidal AI is halted too abruptly, any aromatase enzymes that are still present in the body may become available to begin aromatizing androgens into estrogens again, often at a rapid rate. With exemestane use, there is no such risk. 

Furthermore, exemestane is a perfect drug for post-cycle therapy and HPTA recovery. For instance, studies have demonstrated that exemestane dosed at 25 mg per day increased total testosterone by 60% in only 10 days. There is simply no other aromatase inhibitor that can compare in terms of efficacy for HPTA recovery. All of this makes exemestane a perfect choice for post-cycle therapy as well as on-cycle estrogen control. 

The half-life of exemestane is only about 9 hours, and it clears quickly. However, because of how effective exemestane is at eliminating aromatase enzymes (80–90% after administration), estrogen levels will remain low for up to 72 hours after a single dose of 25mg. 

Post-cycle therapy (PCT)