Letrozole (Femara) is an oral non-steroidal aromatase inhibitor that has been introduced for the adjuvant treatment of hormonally-responsive breast cancer
Estrogens are produced by the conversion of androgens through the activity of the aromatase enzyme. Letrozole blocks production of estrogens in this way by competitive, reversible binding to the heme of its cytochrome P450 unit. The action is specific, and letrozole does not reduce production of mineralo- or corticosteroids. In contrast, the antiestrogenic action of tamoxifen(Tadex,Nolvadex), the major medical therapy prior to the arrival of aromatase inhibitors, is due to its interfering with the estrogen receptor, rather than inhibiting estrogen production.
In the world of bodybuilding where more is often thought to be better, Letrozole stands almost alone as an exception to that rule. Estrogen is necessary for healthy immune function, healthy cholesterol levels, joint health, cognitive function, and even aids in muscle growth. Letrozole simply causes estrogen to be reduced to levels too low to function properly. For most recreational steroid users, Letrozole is going to be too harsh, and cause too many problems. Still, people can use it effectively if they don’t use the manufacturer’s clinical dose (2.5mgs) and instead keep their dose to .25-1mg. Using Letrozole at such a low dose does happen to make it a very good economic choice compared with other aromatase inhibitors.
Letrozole (Femara) can be used to raise LH and FSH (which are hormones which signal your testes to produce more testosterone). It also, of course, will raise your testosterone levels via this mechanism. Again, this is of interest to athletes and bodybuilders for obvious reasons. Letrozole (Femara), of course, can be used for post-cycle-therapy (PCT) to raise test levels, but for various reasons, Tamoxifen(Nolvadex, Tadex) may be a better choice.
In non-cellular systems, Letrozole (Femara) is 2-5 times more potent than anastrozole(Arimidex) and exemestane(Aromasin) in its inhibition of the aromatase enzyme and activity, and in cellular systems it is 10-20x more potent! It also lasts quite a long time in your body, but takes awhile to get going: Letrozole (Femara) has a whopping 2-4 day (!) ½ life, and you need to take Letrozole (Femara) for 60 days to get a steady blood plasma level.
Store in temperature not exceeding 77oF(25oC), away from excess moisture.