Here's a little bit of info from an article I wrote on aromasin that will help give you an idea of how it works and why it is so effective
Aromasin is a suicidal Aromatose inhibitor, which makes it a better choice than other AIs. Exemestane binds with aromatase enzymes and then subsequently permanently disables the enzyme by destroying it.
Aromasin is a steroidal AI which keeps it from negatively affecting your lipids like other non-steroidal AIs. It is also not liver toxic, and can be ran for longer lengths of time without negative effect. This makes it a better option to run on cycle from a pure health standpoint. Aromasin will not hurt your gains on cycle like other AIs, but may actually help them. Another benefit on cycle is that steroidal AIs lower SHBG which increases the ratio of free to bound testosterone. What that means during your cycle is a very positive impact on your gains. This (in a sense) makes your AAS more bio-available.
The half-life of Aromasin is only about 9 hours, and clears quickly. However, because of how effective Exemestane is at eliminating Aromatose enzymes (80-90% after administration), estrogen levels will remain low up to 72 hours after a single dose of 25mg. This is why aromasin is very effective dosed just every other day. In one study, users were still 40% below baseline estrogen values 72 hours after their dose. This is because no more Aromatose can be made until your body produces more Aromatose enzymes. This makes aromasin very versatile for dosing and not require more frequency.
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