Arimidex (chemical name: anastrozole) is an aromatase inhibitor used to treat all stages of hormone receptor-positive breast cancer in post-menopausal women.

Arimidex (chemical name: anastrozole) is an aromatase inhibitor used:

  • to reduce the risk of hormone receptor-positive, early-stage breast cancer coming back (recurring) in post-menopausal women after surgery

  • as a first treatment for hormone receptor-positive, advanced-stage breast cancer in post-menopausal women

  • to treat advanced-stage breast cancer that has
    grown after tamoxifen treatment in post-menopausal women

It’s important to know that Arimidex should not be taken at the same time as tamoxifen.


How Arimidex works

Arimidex works by blocking the enzyme aromatase, which turns the hormone androgen into small amounts of estrogen in the body. This means less estrogen is available to stimulate the growth or hormone receptor-positive breast cancer cells.

Arimidex will not work on hormone receptor-negative breast cancer.


Is Arimidex right for you?

Arimidex is used to treat post-menopausal women diagnosed with either early-stage or advanced-stage, hormone receptor-positive breast cancer.

Arimidex is not commonly used to treat pre-menopausal women.

You should not take Arimidex if you are breastfeeding, pregnant, trying to get pregnant, or if there is any chance that you could be pregnant. Arimidex may cause damage to developing embryos. You should use an effective non-hormonal type of birth control while you are taking Arimidex. Ask your doctor which type of non-hormonal birth control would be best for you. You should use the birth control for at least three weeks after your last dose of Arimidex.


What to expect during Arimidex treatment

Arimidex is a pill taken once per day. It is available as a generic medicine.

In most cases, a post-menopausal woman diagnosed with early-stage, hormone receptor-positive breast cancer would take Arimidex for five years after surgery to reduce the risk of recurrence. After that, if breast cancer had been found in the lymph nodes, called node-positive disease, a woman would take Arimidex or another aromatase inhibitor for an additional five years, for a total of 10 years of hormonal therapy treatment. Doctors call taking hormonal therapy for 10 years after surgery extended adjuvant hormonal therapy.

Researchers are studying whether taking Arimidex for less than five more years after the initial five years offers the same benefits as taking Arimidex for five more years.

If you’ve been diagnosed with advanced-stage, hormone receptor-positive breast cancer, you continue to take Arimidex as long as you are getting benefits from the medicine.


Arimidex side effects

Like almost all breast cancer medicines, Arimidex can cause side effects, some of them severe.

The most common side effects of Arimidex are:

Other serious side effects Arimidex may cause include:

  • Heart problems: In women with pre-existing heart problems caused by narrowed heart arteries, Arimidex increased the risk of heart problems. If you have heart disease, you and your doctor will weigh the risks and benefits of Arimidex for you.

  • Bone loss: Because Arimidex lowers the amount of estrogen in the body, less estrogen reaches bone cells, which can lead to bone thinning and weakening and a higher-than-average risk of breaking a bone. If you’ve been diagnosed with osteopenia or osteoporosis, your doctor may recommend that you take a different hormonal therapy medicine, such as tamoxifen, rather than Arimidex. Your doctor also will likely monitor your bone density while you’re taking Arimidex.

  • High cholesterol: In some cases, Arimidex can increase your blood cholesterol levels. If you have high cholesterol, your doctor will likely monitor your cholesterol levels while you’re taking Arimidex.

Research suggests that up to half of the women prescribed Arimidex or another hormonal therapy medicine stop taking the medicine early, in many cases because of troubling or painful side effects. Still, it’s very important to know that taking hormonal therapy for the prescribed amount of time can reduce the risk of recurrence by 50% and can reduce the risk of dying from breast cancer by about 30%.

If you’re having problematic side effects from taking Arimidex or another hormonal therapy medicine, talk to your doctor right away. There are steps you can take to ease some of the most common side effects:

  • medicines have been shown to reduce the number and severity of hot flashes

  • complementary and alternative therapies, such as acupuncture and mindfulness meditation, have been shown to ease pain, including joint pain

  • exercise has been shown to ease joint pain and increase bone density

You also may be able to switch to a different hormonal therapy medicine or take a different dose.


Paying for Arimidex

If your doctor prescribes Arimidex or generic anastrozole and you have problems paying for it or getting it covered by insurance, the Arimidex Patient Direct program may be able to help you.

Learn more about Paying for Your Care, including information on additional types of financial assistance and cost-lowering tips.


Arimidex (anastrozole) prescribing information. ANI Pharmaceuticals, Inc. USA. Available at:

— Last updated on July 27, 2022, 1:46 PM

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