Anastrozole, sold under the brand name Arimidex among others, is an antiestrogenic medication used in addition to other treatments for breast cancer.

[8] Common side effects of anastrozole include hot flashes, altered mood, joint pain, and nausea.

[8][7] Severe side effects include an increased risk of heart disease and osteoporosis.

[14] The trial suggested that anastrozole is the preferred medical therapy for postmenopausal women with localized estrogen receptor-positive breast cancer.

[7] Serious but rare adverse effects (<0.1% incidence) include skin reactions such as lesions, ulcers, or blisters; allergic reactions with swelling of the face, lips, tongue, and/or throat that may cause difficulty swallowing or breathing; and abnormal liver function tests as well as hepatitis.

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

[4][3] As such, 1 mg/day is considered to be the minimal dosage required to achieve maximal suppression of aromatase with anastrozole.

[3][7] Absorption of anastrozole is linear over a dosage range of 1 to 20 mg/day in humans and does not change with repeated administration.

[5] The medication is eliminated predominantly by metabolism in the liver (83 to 85%) but also by residual excretion by the kidneys unchanged (11%).

[30][31][32][33] Anastrozole was patented by Imperial Chemical Industries (ICI) in 1987 and was approved for medical use, specifically the treatment of breast cancer, in 1995.

[1] Anastrozole is surprisingly ineffective at treating gynecomastia, in contrast to selective estrogen receptor modulators like tamoxifen.

[37] Anastrozole increases testosterone levels in males and has been studied as an alternative method of androgen replacement therapy in men with hypogonadism.

[38][39] However, there are concerns about its long-term influence on bone mineral density in this patient population, as well as other adverse effects.