Letrozole

Letrozole
Clinical data
Trade names	Femara, others
AHFS/Drugs.com	Monograph
MedlinePlus	a698004
License data	US DailyMed: Letrozole;
Routes of; administration	By mouth
Drug class	Aromatase inhibitor; Antiestrogen
ATC code	L02BG04 (WHO) ;
Legal status
Legal status	CA: Schedule VII; UK: POM (Prescription only); US: ℞-only; EU: Rx-only;
Pharmacokinetic data
Bioavailability	99.9%
Protein binding	60%, mainly to albumin
Metabolism	pharmacologically-inactive metabolites Bis(4-cyanophenyl)methanol and 4,4'-dicyanobenzophenone.
Elimination half-life	2 days
Excretion	Kidney
Identifiers
	IUPAC name 4,4'-((1H-1,2,4-triazol-1-yl)methylene)dibenzonitrile;
CAS Number	112809-51-5 ;
PubChem CID	3902;
IUPHAR/BPS	5209;
DrugBank	DB01006 ;
ChemSpider	3765 ;
UNII	7LKK855W8I;
KEGG	D00964 ;
ChEBI	CHEBI:6413 ;
ChEMBL	ChEMBL1444 ;
CompTox Dashboard (EPA)	DTXSID4023202 ;
ECHA InfoCard	100.200.357
Chemical and physical data
Formula	C17H11N5
Molar mass	285.310 g·mol−1
3D model (JSmol)	Interactive image;
	SMILES N#Cc1ccc(cc1)C(c2ccc(C#N)cc2)n3ncnc3;
	InChI InChI=1S/C17H11N5/c18-9-13-1-5-15(6-2-13)17(22-12-20-11-21-22)16-7-3-14(10-19)4-8-16/h1-8,11-12,17H ; Key:HPJKCIUCZWXJDR-UHFFFAOYSA-N ;
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Letrozole, sold under the brand name Femara among others, is an aromatase inhibitor medication that is used in the treatment of breast cancer for post-menopausal women.

It was patented in 1986 and approved for medical use in 1996. In 2021, it was the 222nd most commonly prescribed medication in the United States, with more than 1 million prescriptions. It is on the World Health Organization's List of Essential Medicines.