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What is Arimidex® ? (anastrozole)

Arimidex is a type of hormone therapy called an aromatase inhibitor. It may be used in the treatment of breast cancer in several ways1:

  • As adjuvant (after initial therapy) treatment in postmenopausal women with hormone receptor-positive early breast cancer
  • As first-line treatment in postmenopausal women with hormone receptor positive or unknown hormone receptor status in advanced or metastatic breast cancer
  • As treatment in postmenopausal women with advanced breast cancer who experienced disease progression after treatment with tamoxifen

Anastrozole is manufactured by ANI Pharmaceuticals.

What is the ingredient in Arimidex?

The active ingredient in Arimidex is anastrozole, an aromatase inhibitor.1

How does anastrozole work?

Many breast cancers are hormone receptor-positive. That is, the breast cancer cells have receptors for hormones, such as estrogen, on their surfaces. When estrogen binds to these receptors, it can fuel the growth of the cancer cells and lead to them growing and spreading.

In postmenopausal women, estrogens in the body are created when androgens are converted to estrone and estradiol by the enzyme aromatase. Anastrozole is a selective aromatase inhibitor. It helps stop the action of the enzyme aromatase and significantly lowers the amount of estradiol in the body.1

Possible side effects of anastrozole

The most common side effects experienced by patients with advanced breast cancer taking anastrozole include1:

  • Hot flashes
  • Nausea
  • Weakness or lack of energy
  • Back or bone pain
  • Headache
  • Cough or sore throat
  • Difficulty breathing
  • Swelling of the legs or feet (peripheral edema)

When used as a treatment in early breast cancer, the most common side effects experienced with anastrozole include hot flashes, weakness or lack of energy, joint or back pain, arthritis, sore throat, high blood pressure, depression, nausea, vomiting, rash, osteoporosis, fractures, insomnia, headache, swelling of the legs or feet (peripheral edema), and lymphedema.1

Anastrozole may cause decreases in bone mineral density, which may lead to osteoporosis. Women may need additional screening to monitor their bone density.1

In women with a history of heart artery blockage (ischemic heart disease), anastrozole may increase the risk of cardiovascular events (like heart attacks).1

Anastrozole may increase the levels of cholesterol in the blood. Women may need additional screening to check for increases in cholesterol.1

Things to know about anastrozole

Before starting treatment with anastrozole, women should tell their doctor if they are pregnant, or planning to become pregnant. Anastrozole should not be used in women who are pregnant, as the drug may cause harm to an unborn baby. Anastrozole is only approved for use in women who are postmenopausal.2

Arimidex should not be used by people who have a known allergy to anastrozole.2

Anastrozole should not be used in combination with tamoxifen or estrogen-containing therapies. Women should discuss with their doctor all medications (prescription and over-the-counter), vitamins, and herbal supplements they are taking prior to starting treatment with anastrozole. Some medications or supplements may interfere with each other and may cause side effects.2

Dosing information

Arimidex comes in a tablet that contains 1 mg of anastrozole. The tablet is taken by mouth once daily. It may be taken with or without food.1

For more information, read the full prescribing information of anastrozole.

Patients should take their medication as prescribed by their doctor. Patients should talk to their doctor if they have any questions, or if they have questions regarding their anastrozole regimen.

Written by: Editorial Team | Last reviewed: October 2019.
  1. Arimidex prescribing information. Available at Accessed 9/26/18.
  2. Arimidex product website. Available at Accessed 9/26/18.