Letrozole 2884912 220983143 2008-06-22T14:43:39Z Kccarney 3221173 the correct word "Letrozole" has replace the word "Jamal G...", the work of some vandal {{drugbox | IUPAC_name = 4-[(4-cyanophenyl)-(1,2,4-triazol-1-yl)methyl]benzonitrile | image = Letrozole.svg | CAS_number = 112809-51-5 | ATC_prefix = L02 | ATC_suffix = BG04 | ATC_supplemental = | PubChem = 3902 | DrugBank = APRD01066 | C = 17 | H = 11 | N = 5 | molecular_weight = 285.303 g/mol | smiles = N#Cc1ccc(cc1)C(c1ccc(C#N)cc1)n1cncn1 | bioavailability = 99.9% | protein_bound = 60%, mainly to albumin | metabolism = | elimination_half-life = 2 days | pregnancy_category = | legal_CA =Clinical trial | routes_of_administration = }} '''Letrozole''' ([[International Nonproprietary Name|INN]], trade name '''Femara''') is an oral non-steroidal [[aromatase inhibitor]] that has been introduced for the adjuvant treatment of hormonally-responsive [[breast cancer]]. [[Estrogen]]s 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]], 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. ==FDA-approved use== Letrozole is approved by the [[United States]] [[Food and Drug Administration]] (FDA) for the treatment of local or metastatic breast cancer that is hormone receptor positive or has an unknown receptor status in postmenopausal women. Side effects include signs and symptoms of [[hypoestrogenism]]. There is concern that long term use may lead to [[osteoporosis]], which is why prescriptions of Letrozole are often accompanied by prescriptions of osteoporosis-fighting medication such as [[Fosamax]]. ==Off-label use== It has been used for ovulation induction by fertility doctors since 2001; having less side-effects than [[clomiphene]] citrate ('''Clomid''') for the patient. A Canadian study presented at the [[American Society of Reproductive Medicine]] 2005 Conference suggests that it may increase the risk of birth defects compared with a control group, however a more detailed follow-up study found no basis for concern when letrozole is used for ovulation induction.<ref>Tulandi T, Martin J, Al-Fadhli R, Kabli N, Forman R, Hitkari J, Librach C, Greenblatt E, Casper RF. Congenital malformations among 911 newborns conceived after infertility treatment with letrozole or clomiphene citrate. Fertil Steril. 2006 Apr 28. PMID 16650422</ref> The manufacturer, [[Novartis]], has issued letters to doctors in Canada and the United States reiterating that it is not approved for such a use and is not safe to use with pregnant women or women who may become pregnant. Letrozole has shown to reduce estrogen levels by 98 percent while raising [[testosterone]] levels. The anti-estrogen action of letrozole is preferred by [[Sportsperson|athletes]] and [[bodybuilder]]s for use during a [[steroid cycle]] to reduce bloating due to excess water retention and prevent the formation of [[gynecomastia]] related breast tissue that is a side effect of some [[anabolic steroids]]. Above 5mg/day for extended periods may cause kidney problems.{{Fact|date=March 2008}} Letrozole has also been shown to delay the fusing of the [[epiphyseal plate|growth plates]] in adolescents. This may boost the effectiveness of growth hormone, and thus Letrozole is used to treat adolescents and children with short stature.{{Fact|date=March 2008}} A related agent is [[anastrozole]]. Letrozole has also been used to treat [[endometriosis]].<ref>[http://www.endometriosis.org/ESHRE2005-abbamonte.html Endometriosis ESHRE abstract<!-- Bot generated title -->]</ref> ==References== <references/> ==See also== *[[Aromatase inhibitor]] ==External links== *[http://www.femara.com Femara website] {{Sex hormones}} [[Category:Aromatase inhibitors]] [[es:Letrozol]]