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Trade/other name(s): Arimidex

Why would this drug be used?

Anastrozole is used to treat breast cancer in women who have already gone through menopause and no longer have menstrual periods (postmenopausal women.)

How does this drug work?

Anastrozole belongs to a group of drugs called aromatase inhibitors. It helps keep the body from making estrogen without affecting other hormones. Breast cancers that need estrogen to grow may stop growing or decrease in size.

Before taking this medicine

Tell your doctor…

If you are allergic to anything, including medicines, dyes, additives, or foods.

If you have any serious medical conditions, such as high cholesterol, heart disease, or liver disease (including cirrhosis)

If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. This drug may cause birth defects if either the male or female is taking it at the time of conception or during pregnancy. Check with your doctor about what kinds of birth control can be used with this medicine.

If you are breast-feeding. It is not known whether this drug passes into breast milk. If it does, it could harm the baby.

If you think you might want to have children in the future. This drug has only been tested in women who have gone through menopause, and it may reduce fertility in those who have not. Talk with your doctor about the possible risk with this drug and options that may preserve your ability to have children.

About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

Medicines that contain estrogen may reduce the action of anastrozole. Tamoxifen may also reduce its effects.

Check with your doctor, nurse, or pharmacist about other medicines, vitamins, herbs, and supplements, and whether alcohol can cause problems with this medicine.

Interactions with foods

No serious interactions with food are known at this time. Check with your doctor, nurse, or pharmacist about whether foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Anastrozole is a pill and should be taken once a day, about the same time each day. It can be taken with or without food. The dose is the same for all adults. Take this drug exactly as your doctor tells you to. If you do not understand the instructions, your doctor or nurse can explain them to you.

Store the medicine in a tightly closed container and away from children and pets.


It is important to keep taking this drug, even if you feel well. If you are bothered by side effects, talk to your doctor or nurse to find out if the problems are serious. Many side effects can be managed with help from your doctor.

Very rarely, this drug may cause blood clots. This can take the form of clots in arms or legs (deep vein thrombosis), heart attack, stroke, or a blockage in the lungs. Call your doctor or nurse right away if you notice pain in your lower leg (calf), redness or swelling of your arm or leg, shortness of breath, chest pain, or trouble speaking or moving.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.



lower energy level

Less common



mild diarrhea

increased or decreased appetite


hot flashes

vaginal dryness

pain in bones and joints

increased osteoporosis (thinning bones)

higher risk of broken bones (fracture)

thinning hair

mood disturbances


blood clots with redness or mild swelling of arms, legs and ankles, pain in leg or calf, shortness of breath, pain in the chest, trouble moving or speaking*

allergic reaction with itchy welts, swelling mouth or throat, and trouble breathing

*See "Precautions" section for more detailed information.

There are other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved in 1995

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 12/02/2009
Last Revised: 12/02/2009