Cytadren, at moderate doses, is a fairly effective inhibitor of aromatase and a weak inhibitor of desmolase (an enzyme needed for the production of all steroids), and at higher doses becomes an effective inhibitor of desmolase. It is therefore useful when using aromatizable steroids, though it is not the drug of choice for this purpose.
Inhibition of desmolase — the undesired side effect of Cytadren — will lead, at least temporarily, to decreased production of cortisol. Contrary to the other claims, there is no evidence, nor good reason to believe, that reducing cortisol below normal would be of benefit to the weight training athlete, and considerable evidence that it is a bad idea. Thus, desmolase inhibition is to be avoided.
The claim that Cytadren significantly inhibits natural production of testosterone is not correct. The desmolase step is rate limiting for the production of cortisol, but not for testosterone: thus, a slowing of desmolase activity does not slow production of testosterone significantly. However, the conclusion that natural athletes should not use Cytadren is correct, but for a different reason. Natural athletes have no need of the antiaromatase activity, and the anti-desmolase activity, reducing cortisol below normal, is not desirable. It would only be desirable if cortisol levels were abnormally high, which should not be the case.
The claim that 2-4 tablets per day (500-1000 mg) should be taken is extraordinarily bad advice. I do not believe that more than 250 mg/day should be taken, and that should be taken very carefully, divided into 125 mg (half a tab) in the morning, and 62.5 mg (quarter tab) six and twelve hours after that. The two days on on, two days off idea is also not a good one, since that gives no antiaromatase activity half of the time.
It has been demonstrated that 250 mg/day is not much less effective than 1000 mg/day in inhibiting aromatase, but the smaller dose results in much less desmolase inhibition.
If desmolase has been substantially inhibited and then this is suddenly discontinued, cortisol rebound occurs. While the dosing protocol given above generally allows the user to stop "cold turkey," since desmolase inhibition is low, tapering down is nonetheless a good idea, and is in fact necessary if, inadvisedly, doses higher than recommended were used.