white to off-whitecrystalline powder
Letrozole(112809-51-5) is an oral non-steroidal aromatase inhibitor that has been introduced for the adjuvant treatment of hormonally-responsive breast cancer.
A nonsteroidal aromatase inhibitor structurally related to Fadrozole. Antineoplastic
CAS DataBase Reference
112809-51-5(CAS DataBase Reference)
Letrozole(112809-51-5) 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 medications such as bisphosphonates.
R36/37/38:Irritating to eyes, respiratory system and skin .
S26:In case of contact with eyes, rinse immediately with plenty of water and seek medical advice .
S36:Wear suitable protective clothing .
Hazardous Substances Data
112809-51-5(Hazardous Substances Data)
Letrozole (trade name: Femara) is an orally active nonsteroidal aromatase inhibitor. As a competitive inhibitor of the aromatase, Letrozole inhibits the conversion of androgens to estrogen (estrogen stimulates breast tissues and breast cancer reoccurrence) and gonadal steroidogenesis. It can be used for the treatment of breast cancer that is hormonally-responsive or has an unknown receptor status in postmenopausal women. Besides this, Letrozole also has some off-label use such as ovarian stimulation, pretreatment of termination of pregnancy, treatment of gynecomastia, treatment of endometriosis, and promoting spermatogenesis for male patients of nonobstructive azoospermia.
Letrozole is part of a new generation of highly selective aromatase inhibitors and is an artificially synthesized benzotriazole derivative. Letrozole inhibits aromatase to lower estrogen levels, thus preventing estrogen from stimulating tumor growth. Its in vivo activity is 150-250 times stronger than that of first generation aromatase inhibitor Amarante. As it is highly selective, it will not impact glucocorticoid, mineralocorticoid and thyroid functions; even at high dosages, it will not have any inhibiting effects on adrenal corticosteroid secretion, giving it a high treatment index. Letrozole has no latent toxicity towards any bodily systems and target organs, has no mutagenicity and carcinogenic effects, has minimal toxic side effects, is well-tolerated, and has stronger anticancer effects than other aromatase inhibitors and antiestrogen drugs. Letrozole is suitable for advanced breast cancer postmenopausal patients who have not responded to estrogen-suppressing treatment and for early breast cancer treatment. It is used to treat postmenopausal patients with advanced breast cancer and serves as a second-line treatment to follow unsuccessful antiestrogen treatment. Compared to the current standard Tamoxifen treatment, Letrozole can better prevent the risk of breast cancer recurrence.
Absorption of oral letrozole is rapid and complete and steady state is achieved in 2–6 weeks with administration of letrozole 2.5mg once daily. The major route of elimination of letrozole is via metabolism to a pharmacologically inactive carbinol metabolite. The cytochrome P450 (CYP) 3A4 and CYP2A6 isozymes metabolize letrozole to a pharmacologically inactive carbinol metabolite. Renal excretion of a glucuronide conjugate of the carbinol metabolite of letrozole represents the major route of drug clearance.
Randomized grouping studies have shown that daily oral ingestion of 2.5mg Letrozole leads to a 33% rate of drug-related negative reactions, a percentage much lower than AG group’s 46%. Negative reactions to Letrozole are mostly mild or moderate, consisting mostly of nausea (2-9%), headache (0-7%), bone pain (4-10%), hot flashes (0-9%) and weight gain (2-8%). Other uncommon side effects include constipation, diarrhea, itching, rash, joint pain, chest pain, abdominal pain, fatigue, insomnia, dizziness, edema, high blood pressure, arrhythmia, thrombosis, dyspnea, vaginal bleeding, etc.
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