Arimidex

Brand name for anastrozole, an oral antiestrogen. Arimidex inhibits the enzyme aromatase in the adrenal glands that produces the estrogens (estradiol and estrone) and thereby lowers their levels. It works by decreasing the amount of estrogen the body makes. This can slow or stop the growth of many types of breast cancer cells that need estrogen to grow.

A drug that inhibits the enzyme aromatase and by that means lowers the level of the estrogen estradiol. Aromatase inhibitors represent a class of antiestrogens.

Aromatase catalyzes the conversion of testosterone (an androgen) to estradiol (an estrogen) in many tissues including the adrenal glands, ovaries, placenta, testicles, adipose (fat) tissue, and brain. Estrogen is produced directly by the ovaries and is also made by the body using aromatase. Aromatase inhibitors cannot do anything about estrogen produced by the ovaries, but they do interfere with the body’s use of aromatase.

The growth of many breast cancers is promoted by estrogens. Most estrogen after menopause comes from the action of aromatase. Aromatase inhibitors may therefore be used to treat estrogen-dependent tumors after the menopause. Aromatase inhibitors are used mostly in women who have reached menopause, when the ovaries are no longer producing estrogen.

The aromatase inhibitors approved by the US Food and Drug Administration include anastrazole (Arimidex), exemestane (Aromasin), and letrozole (Femara).