Letrozole

Letrozole
Clinical data
Trade namesFemara, others
AHFS/Drugs.comMonograph
MedlinePlusa698004
License data
Routes of
administration		By mouth
Drug classAromatase inhibitor; Antiestrogen
ATC code
Legal status
Legal status
Pharmacokinetic data
Bioavailability99.9%
Protein binding60%, mainly to albumin
Metabolismpharmacologically-inactive metabolites Bis(4-cyanophenyl)methanol and 4,4'-dicyanobenzophenone.[3]
Elimination half-life2 days[3]
ExcretionKidney[3]
Identifiers
  • 4,4'-((1H-1,2,4-triazol-1-yl)methylene)dibenzonitrile
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.200.357 Edit this at Wikidata
Chemical and physical data
FormulaC17H11N5
Molar mass285.310 g·mol−1
3D model (JSmol)
  • N#Cc1ccc(cc1)C(c2ccc(C#N)cc2)n3ncnc3
  • 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 checkY
  • Key:HPJKCIUCZWXJDR-UHFFFAOYSA-N checkY
  (verify)

Letrozole, sold under the brand name Femara among others, is an aromatase inhibitor medication that is used in the treatment of breast cancer.[1]

It was patented in 1986 and approved for medical use in 1996.[4] In 2021, it was the 222nd most commonly prescribed medication in the United States, with more than 1 million prescriptions.[5][6] It is on the World Health Organization's List of Essential Medicines.[7]


  1. ^ a b "Femara- letrozole tablet, film coated". DailyMed. 13 May 2022. Retrieved 28 August 2022.
  2. ^ "List of nationally authorised medicinal products : Active substance(s): letrozole : Procedure No. PSUSA/00001842/202110" (PDF). Ema.europa.eu. Retrieved 30 June 2022.
  3. ^ a b c "Letrozole". 24 January 2003. Archived from the original on 24 January 2003. Retrieved 30 June 2022.
  4. ^ Fischer J, Ganellin CR (2006). Analogue-based Drug Discovery. John Wiley & Sons. p. 516. ISBN 9783527607495.
  5. ^ "The Top 300 of 2021". ClinCalc. Archived from the original on 15 January 2024. Retrieved 14 January 2024.
  6. ^ "Letrozole - Drug Usage Statistics". ClinCalc. Retrieved 14 January 2024.
  7. ^ World Health Organization (2023). The selection and use of essential medicines 2023: web annex A: World Health Organization model list of essential medicines: 23rd list (2023). Geneva: World Health Organization. hdl:10665/371090. WHO/MHP/HPS/EML/2023.02.