What You Need to Know About the Drug Anastrozole

Medically Reviewed by Poonam Sachdev on November 12, 2021

Anastrozole, sold as Arimidex, is an oral hormone therapy pill used to treat women who are diagnosed with breast cancer after menopause. It's prescribed for women with early- or advanced-stage breast cancer after treatments like surgery, chemotherapy, and radiation.

Some breast cancers, called hormone-receptor-positive breast cancers, grow due to the hormone estrogen. Anastrozole decreases estrogen levels in the body and slows or reverses breast cancer growth.

Anastrozole Is Superior to Drugs Like Tamoxifen

Tamoxifen used to be the drug of choice to treat advanced-stage breast cancer in women after menopause. It works by attaching itself to the estrogen receptors on cancer cells. But it can’t completely decrease the growth effects of estrogen on cancer cells.

Anastrozole prevents estrogen production in the body. It's more effective than tamoxifen in reducing breast cancer growth. Anastrozole is often used to treat patients whose breast cancer reappears or continues to grow after tamoxifen treatment.

Anastrozole Helps in Breast Cancer Prevention

Anastrozole is an effective breast cancer prevention drug, as well. A recent study revealed that the drug greatly reduced invasive and non-invasive breast cancer over a follow-up period of 5 years, without any new side effects. Further research and follow-up are needed to study how anastrozole affects breast cancer mortality. 

Anastrozole is the drug of choice for breast cancer prevention for the following reasons:

  • It reduces the risk of cancer coming back.
  • It reduces the risk of cancer spreading to other parts of the body.
  • It reduces the risk of cancer growing in the other breast.

Other Considerations

Anastrozole is a 1-mg oral pill usually taken once a day at the same time each day. You can take it with or without food as recommended by your doctor. Regular use of the drug over 5 years helps in faster recovery from breast cancer. The time of use can vary depending on your condition.

The drug doesn’t work on hormone-receptor-negative breast cancer and it shouldn't be taken with drugs like tamoxifen. Your doctor will advise you not to take the drug if you are breastfeeding, pregnant, or expecting pregnancy.

Show Sources

SOURCES: “Arimidex.”

Journal of Clinical Oncology: “Anastrozole Is Superior to Tamoxifen as First-Line Therapy for Advanced Breast Cancer in Postmenopausal Women: Results of a North American Multicenter Randomized Trial.”

Lancet: “Use of anastrozole for breast cancer prevention (IBIS-II): long-term results of a randomised controlled trial.”

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