Anastrozole, sold under the brand name Arimidex among others, is a medication used in addition to other treatments for breast cancer.[1] Specifically it is used for hormone receptor-positive breast cancer.[1] It has also been used to prevent breast cancer in those at high risk.[1] It is taken by mouth.[1]

Clinical data
Trade namesArimidex, others
License data
  • US: D (Evidence of risk) [1]
Routes of
By mouth (tablets)
Drug classAromatase inhibitor; Antiestrogen
ATC code
Legal status
Legal status
Pharmacokinetic data
Protein binding40%
MetabolismLiver (85%)
Elimination half-life46.8 hours[2]
ExcretionUrine (11%)
CAS Number
PubChem CID
ECHA InfoCard100.129.723 Edit this at Wikidata
Chemical and physical data
Molar mass293.366 g/mol g·mol−1
3D model (JSmol)
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Common side effects include hot flushes, altered mood, joint pain, and nausea.[1] Severe side effects include an increased risk of heart disease and osteoporosis.[1] Use during pregnancy is known to harm the baby.[1] Anastrozole is in the aromatase-inhibiting family of medications.[1] It works by blocking the creation of estrogen.[1]

Anastrozole was patented in 1987 and approved for medical use in 1995.[4] It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system.[5] Anastrozole is available as a generic medication.[1] The wholesale cost in the developing world is about US$1.92–30.60 a month.[6] In the United States the wholesale cost is about $3.81 per month.[7] In 2016 it was the 224th most prescribed medication in the United States with more than 2 million prescriptions.[8]


Anastrozole works by reversibly binding to the aromatase enzyme, and through competitive inhibition blocks the conversion of androgens to estrogens in peripheral (extragonadal) tissues.[9]


The ATAC trial was of localized breast cancer and women received either anastrozole, tamoxifen, or both for five years, followed by five years of follow-up.[10] After more than 5 years the group that received anastrozole had better results than the tamoxifen group.[10] The trial suggested that anastrozole is the preferred medical therapy for postmenopausal women with localized estrogen receptor (ER) positive breast cancer.[10]


  1. ^ a b c d e f g h i j k "Anastrozole". The American Society of Health-System Pharmacists. Archived from the original on 21 December 2016. Retrieved 8 December 2016.
  2. ^ Mauras N, Bishop K, Merinbaum D, Emeribe U, Agbo F, Lowe E (August 2009). "Pharmacokinetics and pharmacodynamics of anastrozole in pubertal boys with recent-onset gynecomastia". J. Clin. Endocrinol. Metab. 94 (8): 2975–8. doi:10.1210/jc.2008-2527. PMID 19470631.
  3. ^ "anastrozole". Chemical Entities of Biological Interest (ChEBI). European Molecular Biology Laboratory. Archived from the original on 2011-09-22. Retrieved 2011-08-14.
  4. ^ Fischer, Janos; Ganellin, C. Robin (2006). Analogue-based Drug Discovery. John Wiley & Sons. p. 516. ISBN 9783527607495. Archived from the original on 2016-12-20.
  5. ^ "WHO Model List of Essential Medicines (19th List)" (PDF). World Health Organization. April 2015. Archived (PDF) from the original on 13 December 2016. Retrieved 8 December 2016.
  6. ^ "Anastrozole". International Drug Price Indicator Guide. Retrieved 8 December 2016.
  7. ^ "NADAC as of 2016-12-07 |". Centers for Medicare and Medicaid Services. Archived from the original on 21 December 2016. Retrieved 18 December 2016.
  8. ^ "The Top 300 of 2019". Retrieved 22 December 2018.
  9. ^ Simpson ER (September 2003). "Sources of estrogen and their importance". J. Steroid Biochem. Mol. Biol. 86 (3–5): 225–30. doi:10.1016/S0960-0760(03)00360-1. PMID 14623515.
  10. ^ a b c Howell A; Cuzick J; Baum M; et al. (2005). "Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer". Lancet. 365 (9453): 60–2. doi:10.1016/S0140-6736(04)17666-6. PMID 15639680.[non-primary source needed]