IUPAC_name = 2- [3-(1-cyano-1-methyl-ethyl)- 5-(1"H"-1,2,4-triazol-1-ylmethyl)phenyl] - 2-methyl- propanenitrile

CAS_number = 120511-73-1
ChemSpiderID = 2102
ATC_prefix = L02
ATC_suffix = BG03
ATC_supplemental =
PubChem = 2187
DrugBank = APRD00016
C = 17 | H = 19 | N = 5
molecular_weight = 293.366 g/mol
smiles = N#CC(C)(C)c1cc(Cn2cncn2)cc(c1)C(C)(C)C#N
bioavailability = 83-85%
protein_bound = 40%
metabolism = 85% hepatic
excretion = 11% renal
elimination_half-life = 72 hours
pregnancy_us = D
pregnancy_category =
legal_status = Rx only (U.S.)
routes_of_administration = oral

Anastrozole (INN, trade name: Arimidex) is a drug indicated in the treatment of breast cancer in post-menopausal women. Anastrozole belongs in the class of drugs known as aromatase inhibitors and is used for adjuvant therapy (i.e. following surgery) and metastatic breast cancer. Arimidex is manufactured and marketed by AstraZeneca.

The ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial represents a long-term follow-up study of 9366 women with localized breast cancer who received either anastrozole, tamoxifen, or both. [cite journal |author=Howell A, Cuzick J, Baum M, "et al" |title=Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer |journal=Lancet |volume=365 |issue=9453 |pages=60–2 |year=2005 |pmid=15639680 |doi=10.1016/S0140-6736(04)17666-6] After more than 5 years the group that received anastrozole had significantly better clinical results than the tamoxifen group. The trial suggested that anastrozole is the preferred medical therapy for postmenopausal women with localized breast cancer that is estrogen receptor positive.

Anastrozole is currently under patent protection in the US, however the generic form is available in other markets that do not allow brand name manufacturers such extended protection.

Mechanism of Action

Anastrozole inhibits the enzyme aromatase, which is responsible for converting androgens to estrogens. Anastrozole binds reversibly to the aromatase enzyme through competitive inhibition.

Elevated levels of estrogens may increase the severity of breast cancer, as sex hormones can cause hyperplasia and differentiation at estrogen receptor sites.

Usage for men

While officially indicated for women, this drug has proven effective in the off-label use of reducing estrogens (in particular and more importantly, estradiol) in men. Excess estradiol in men can cause benign prostatic hyperplasia, gynecomastia, and symptoms of hypogonadism. Some athletes and body builders will also use anastrozole as a part of their steroid cycle to reduce and prevent symptoms of excess estrogens; in particular, gynecomastia and water retention.

Study data currently suggests that dosages of 0.5mg to 1mg a day reduce serum estradiol by about 50% in men, which differs from the typical reduction in postmenopausal women. However the reduction may be different for men with grossly elevated estradiol (clinical data is currently lacking).

Usage for children

This drug is frequently used in the treatment of growth disorder affected children to stop or slow the onset of puberty. The treatment of the growth disorder is through hormones which may trigger the early onset of puberty (precocious puberty). At the onset of puberty the bone growth plates begin to close. This can occur in children as young as 5 years old so for children severely behind in growth, the opportunity for increased growth is diminished. Arimidex is shown to slow or stop this process.


External links

* [ - Information about Arimidex and breast cancer]

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