Anastrozole (INN, trade name: Arimidex®) is a drug indicated in the treatment of breast cancer in post-menopausal women. It is used both in adjuvant therapy (i.e. following surgery) and in metastatic breast cancer. It has the effect of decreasing the amount of estrogens that the body makes.

Anastrozole belongs in the class of drugs known as aromatase inhibitors. It inhibits the enzyme aromatase, which is responsible for converting androgens (produced by women in the adrenal glands) to estrogens.

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.^[1] 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.

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.

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