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Drug class
Fulvestrant, a steroidal antiestrogen and a drug used in the treatment of breast cancer.
Class identifiers
SynonymsEstrogen antagonists; Estrogen blockers; Estradiol antagonists
UseBreast cancer; Infertility; Male hypogonadism; Gynecomastia; transgender men
ATC codeL02BA
Biological targetEstrogen receptor
Chemical classSteroidal; Nonsteroidal (triphenylethylene, others)
External links
In Wikidata

Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or inhibiting or suppressing estrogen production.[1][2] Antiestrogens are one of three types of sex hormone antagonists, the others being antiandrogens and antiprogestogens.[3]

Types and examples

Antiestrogens include selective estrogen receptor modulators (SERMs) like tamoxifen, clomifene, and raloxifene, the ER silent antagonist and selective estrogen receptor degrader (SERD) fulvestrant,[4][5] aromatase inhibitors (AIs) like anastrozole, and antigonadotropins including androgens/anabolic steroids, progestogens, and GnRH analogues.

Although aromatase inhibitors and antigonadotropins can be considered antiestrogens by some definitions, they are often treated as distinct classes.[6] Aromatase inhibitors and antigonadotropins reduce the production of estrogen, while the term "antiestrogen" is often reserved for agents reducing the response to estrogen.[7]

Medical uses

Antiestrogens are used for:

Side effects

Side effects of antiestrogens include hot flashes, osteoporosis, breast atrophy, vaginal dryness, and vaginal atrophy. In addition, they may cause depression and reduced libido.


Ethamoxytriphetol (MER-25) was the first antagonist of the ER to be discovered,[8] followed by clomifene and tamoxifen.[9][10]


  1. ^ "Definition of antiestrogen - NCI Dictionary of Cancer Terms, Definition of antiestrogen - NCI Dictionary of Cancer Terms".,
  2. ^ "antiestrogen" at Dorland's Medical Dictionary
  3. ^ Judi Lindsley Nath (2006). Using Medical Terminology: A Practical Approach. Lippincott Williams & Wilkins. pp. 977–. ISBN 978-0-7817-4868-1.
  4. ^ Eckhard Ottow; Hilmar Weinmann (8 September 2008). Nuclear Receptors as Drug Targets. John Wiley & Sons. pp. 164–165. ISBN 978-3-527-62330-3.
  5. ^ Bruce A. Chabner; Dan L. Longo (8 November 2010). Cancer Chemotherapy and Biotherapy: Principles and Practice. Lippincott Williams & Wilkins. pp. 660–. ISBN 978-1-60547-431-1.
  6. ^ Riggins RB, Bouton AH, Liu MC, Clarke R (2005). "Antiestrogens, aromatase inhibitors, and apoptosis in breast cancer". Vitam. Horm. Vitamins & Hormones. 71: 201–37. doi:10.1016/S0083-6729(05)71007-4. ISBN 9780127098715. PMID 16112269.
  7. ^ Thiantanawat, Apinya; Long, Brian; Brodie, Angela (2003-11-15). "Signaling Pathways of Apoptosis Activated by Aromatase Inhibitors and Antiestrogens". The Journal of Cancer Research. Retrieved 2015-04-13.
  8. ^ Philipp Y. Maximov; Russell E. McDaniel; V. Craig Jordan (23 July 2013). Tamoxifen: Pioneering Medicine in Breast Cancer. Springer Science & Business Media. pp. 7–. ISBN 978-3-0348-0664-0.
  9. ^ V Craig Jordan (27 May 2013). Estrogen Action, Selective Estrogen Receptor Modulators and Women's Health: Progress and Promise. World Scientific. pp. 7, 112. ISBN 978-1-84816-959-3.
  10. ^ Walter Sneader (23 June 2005). Drug Discovery: A History. John Wiley & Sons. pp. 198–199. ISBN 978-0-471-89979-2.

External links

 This article incorporates public domain material from the U.S. National Cancer Institute document: "Dictionary of Cancer Terms".