What is Letrozole?
The new aromatase inhibitor, Letrozole, reversibly, inhibits the enzyme responsible for estrogen biosynthesis. By decreasing the estrogen levels in the body it may release the hypothalamus and/or pituitary from the negative feed back of estrogen on the release of gonadotropins. This will result in an increase in endogenous FSH and LH, which stimulate the development of ovarian follicles. This is similar to the proposed mechanism of action of clomiphene citrate. However, Letrozole may have another peripheral mechanism of action directly in the ovaries. Letrozole is eliminated from the body in a few days after last administration (in contrast to CC which may last up to few months). Also, it does not have a direct antiestrogen action by itself as in CC. So there should be no unwanted peripheral antiestrogen effects on the endometrium, the cervix…etc. The commercial name of Letrozole is Femara. It is available in 2.5 & 5 mg tablets. It is a drug that was developed to inhibit the estrogen p
