What Is Arimidex® (anastrozole)?

Reviewed by: HU Medical Review Board | Last reviewed: June 2023

Arimidex® (anastrozole) is a type of hormone therapy called an aromatase inhibitor. It may be used in the treatment of breast cancer in several ways:1

  • 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

What are the ingredients in Arimidex?

The active ingredient in Arimidex is anastrozole.1

How does anastrozole work?

Many breast cancers are hormone receptor-positive. That means the breast cancer cells have receptors for hormones, such as estrogen, on their surfaces. When estrogen sticks to these receptors, it can fuel the growth of the cancer cells. This leads 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 helps stop the action of the aromatase. This lowers the amount of estradiol in the body.1

What are the possible side effects?

The most common side effects of anastrozole, depending on the specific form of breast cancer being treated, include:1

Anastrozole may also cause serious side effects, including:1

  • Increased blood cholesterol
  • Skin lesions, ulcers, or blisters
  • Severe allergic reactions like trouble breathing and swelling of the face, lips, and throat
  • Liver problems

If you have signs of an allergic reaction while taking anastrozole, call 9-1-1 right away.

These are not all the possible side effects of anastrozole. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with anastrozole.

Other things to know

Anastrozole may cause decreases in bone mineral density. This may lead to osteoporosis. Your doctor may monitor your bone density before and during treatment with anastrozole.1

Anastrozole may increase the levels of cholesterol in the blood. Your doctor may monitor your cholesterol before and during treatment with anastrozole.1

Before starting anastrozole, tell your doctor if you:1,2

  • Have not finished menopause
  • Are allergic to any of the ingredients in the drug
  • Have current or prior heart problems
  • Have osteoporosis
  • Have high cholesterol

Anastrozole can harm an unborn baby. If you can become pregnant, you should use birth control during treatment and for some time after the last dose of anastrozole. You should also not breastfeed during treatment with anastrozole and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking anastrozole.1,2

Anastrozole should not be used in combination with tamoxifen or drugs that contain estrogen.1,2

Before beginning treatment for breast cancer, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

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

By providing your email address, you are agreeing to our privacy policy.