What is Arimidex®?

Arimidex® is a chemotherapy medication prescribed for the treatment of estrogen-dependent breast cancers. The drug’s mechanism of action is to reduce the body’s levels of estrogen and stop the growth of breast cancer cells that rely on a consistent supply of estrogen. Arimidex® is a brand name for a generic drug called anastrozole.

This anticancer agent is similar in principle to hormone replacement therapy used by women who are going through menopause. In both cases, the intent of the treatment is to moderate the amount of estrogen available for use in the body. Hormone replacement therapy increases the amount of estrogen, but breast cancer drugs such as Arimidex® are given to reduce available estrogen.

Estrogen-reducing drugs can be highly effective in the treatment of certain types of breast cancer. This is because some breast cancers actually are dependent on having a consistent supply of estrogen available for use. In women who are more than 45 years old, the majority of breast cancers are dependent on estrogen in this way, because the cancers' initial development is triggered by the hormone.

Arimidex® is a type of drug called an aromatase inhibitor. This means it inhibits the activity of an enzyme called aromatase. In postmenopausal women, this enzyme converts hormones called androgens into estrogen. Aromatase-inhibiting drugs prevent the growth of estrogen-dependent breast cancers by reducing the supply of available estrogen. These types of drugs can slow the growth of these breast cancers and are capable of causing tumor shrinkage.

Not all women are suitable candidates for this medication. For example, late-stage cancers usually are unresponsive to aromatase inhibitors. In addition, these drugs generally are not suitable for use in premenopausal women. This is because in premenopausal women, most of the body’s estrogen is produced in the ovaries, rather than via conversion of androgens by the aromatase enzyme.

Arimidex® can cause many side effects, most of which are unpleasant or moderately painful, rather than being specifically harmful. The most common side effects are headaches, nausea, vomiting, vaginal dryness, vaginal bleeding, hot flushes, diarrhea, skin rashes, muscle and joint pain and lack of energy.

One of the most serious long-term consequences is that this medication can cause loss of bone density, leading to an increased risk of bone fractures. To combat this effect, other medications can be used to prevent severe bone loss. For example, statins can be prescribed in conjunction with an aromatase inhibitor. This approach reduces the cardiovascular risks of estrogen loss as well as bone fracture risks.

Other possible side effects include swollen glands, speech problems, balance problems, sudden confusion and sudden numbness or weakness of the body. Not all of these side effects are indicators of a serious problem. All of them, however, should be reported to a doctor.