Letrozole

[Antò]

(femara)

Letrozole (Femara) is the chemical name of Novartis´ selective third generationAromatase Inhibitor (AI). This drug was developed to fight breast cancer by inhibiting the aromatization. It is usually used as a part of an aggressive treatment in post-menopausal women, to fight and reverse the spread of breast cancer after other treatments (such as Tamoxifen therapy) has failed. It´s probably the most efficient product on the market for this purpose currently (5) It is very similar in structure and action to it´s predecessor Arimidex.
Letrozole (Femara) also does quite a few things which would be of interest to both bodybuilders and athletes. Firstly, it has been shown to reduce estrogen levels by 98% or greater (1). In at least one documented incidence, Letrozole (Femara) reduced estrogen in the test subject to undetectable levels, and increased LH, FSH and SHBG (4). Clearly this is all of interest to bodybuilders, as less estrogen in the body means less chance of certain side effects such as water-retention, Gynocomastia, and acne. This makes Letrozole (Femara) an appropriate choice for even the heaviest bulking or cutting cycles including harsh androgens. Also, if you are a competitive bodybuilder, Letrozole (Femara) is a must have product for contest prep; no other Ancillary compound will produce a dry and tight look like Letro will.
An effective dose of Letrozole (Femara) is .25-.5mg/day (I use .25mgs/day), but be forewarned, if you go over that amount, it can kill your sex drive. Also worth noting is that there´s a rebound effect on your estrogen when you come off Letrozol. Maximum inhibition of the aromatase enzyme has been found to happen at doses as low as 100mcg! (2)
Letrozole (Femara)´s effects on serum lipids (cholesterol, both HDL and LDL) are, in the words of one researcher: "inconsistent. " Clearly, however, you´ll eventually suffer an impaired lipid profile and immune system if you keep your estrogen levels too low for too long. Your sex drive will also probably suffer from extraordinarily low levels of estrogen present.
As previously mentioned, 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 (6) 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 may be a better choice. Still, I have successfully used Letrozole (Femara) for this purpose.
How good is this compared with Aromasin and Arimidex, it´s too other main rivals? Well, In non-cellular systems, Letrozole (Femara) is 2-5 times more potent than anastrozole and exemestane 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 (8).
Those are impressive numbers, but here´s one of the most interesting things about Letrozole (Femara):
It may reduce/eliminate/reverse existing gynocomastia!
In a study conducted on mice (*no, I know it´s not perfect), gyno-like-changes in the mammary gland were totally destroyed! Here´s a direct quote from that study:

"Our results also indicate aromatase overexpression-induced changes in mammary glands can be abrogated [destroyed] with very low concentrations of the aromatase inhibitor, Letrozole (Femara)."(7)

In addition, I´ve used Letro to get rid of my own gyno, as has a friend of mine, and we both used it at a dose of 2.5mgs/day, tapering down to .25mgs/day, and then finally off..the gyno never returned in both our cases.
I´d say that this stuff is pretty great, considering its availability and cost (when you consider the fact that .25mgs/day is more than enough protection from estrogen-related sides on most cycles), not to mention it´s overall utility for a variety of functions (destroying gyno, preventing estrogenic sides, and for PCT).
References:

1. Clin Cancer Res. 2005 Apr 15;11(8):2809-21.
2. J Clin Endocrinol Metab. 1995 Sep;80(9):2658-60.
3. Eur J Obstet Gynecol Reprod Biol. 2002 Nov 15;105(2):161-5
4. Epilepsy Behav. 2004 Apr;5(2):260-3
5. Semin Oncol. 2004 Dec;31(6 Suppl 12):3-8.
6. Diabetes Obes Metab. 2005 May;7(3):211-5.
7. J Steroid Biochem Mol Biol. 2001 Dec;79(1-5):27-34. Aromatase overexpression transgenic mice model: cell type specific expression and use of Letrozole (Femara) to abrogate mammary hyperplasia without affecting normal physiology.
8. (Clin Cancer Res. 2003 Jan;9(1 Pt 2):468S-72S.).