In contrast to Arimidex Anastrozole and Femara Letrozole which work by reversibly blocking access to the aromatase enzyme, Aromasin actually inactives individual enzyme molecules when it binds to them.
There is really neither advantage nor disadvantage to this different mode of action. As with all aromatase inhibitors, Aromasin should be dosed to achieve optimal estradiol levels, not the lowest possible levels. When dosed correctly and achieving the same estradiol levels, it doesn’t make a difference what inhibition mechanism was used.
Aromasin Exemestan is usually supplied in 25 mg tablets. Dosing of Aromasin in anabolic steroid cycles is most commonly 12.5 mg every other day, 12.5 mg daily, or at most 25 mg daily.
I have never derived exact formulas for adjustment of dose according to change in amount of aromatizable steroids. Most likely there really is no universal formula. As general advice however, make a reasonable estimate which provides some increase to account for increased amount of aromatizable steroids, but without exceeding the recommended range unless blood testing proves that necessary.
Some use Aromasin during PCT, but I’d do this only if blood testing shows elevated estradiol levels. If that’s the case, then Aromasin is to a small extent actually the preferred aromatase inhibitor over Arimidex Anastrozole or letrozole in this instance, because the other two may have some interaction with the metabolism of SERMs, while Aromasin does not.
Arimidex, letrozole, and Aromasin all are capable of working well and predictably for estrogen control. If already experienced with a given aromatase inhibitor, I recommend continuing with it, as personal dosing is already understood. If you have not yet tried any, then any of them can be effective.