Letrozole – competitive non-steroidal aromatase inhibitor. Aromatase – an enzyme that converts androgens (adrenal) to estrone and estradiol in postmenopausal women. Taking into account that in some cases tumor tissue growth depends on the presence of estrogen, which in postmenopausal formed mainly only involving aromatase use of aromatase inhibitors to reduce estrogen levels and allow for tumor response to therapy.
In animal studies, letrozole resulted in the use of uterine weight and decrease of tumor regression (hormone-dependent) with an efficiency similar to ovariectomy. Thus the therapy letrozole (unlike ovariectomized) is not marked increase in serum levels of follicle stimulating hormone.
Letrozole selectively inhibits the production of steroids in the gonads, without affecting the production of corticosteroids by the adrenal glands and mineralokortikosteroidov.
Aromatase inhibition mechanism is realized through competitive binding with heme letrozole cytochrome P450, thereby reducing the biosynthesis of estradiol in all tissues of the body.
The therapy with letrozole marked decrease in serum levels of estradiol, estrone and estrone sulfate without significantly affecting the synthesis of aldosterone and corticoids, and thyroid hormones.
Perhaps: headache, nausea, peripheral edema, fatigue, hot flashes, thinning hair, skin rash, vomiting, dyspepsia, increased body weight, musculoskeletal pain, anorexia, vaginal bleeding, Leucorrhœa, constipation, dizziness, increased appetite, increased sweating .
Rare: shortness of breath, thrombophlebitis, bleeding from the vagina.
Side effects of substance Letrozole
Headache, dizziness, weakness, nausea, vomiting, change in appetite (usually decline), obstipation, peripheral edema, hot flushes, myalgia, ossalgia, weight changes, hair thinning, gynecological bleeding, spotting from the vagina, skin rashes.