Anastrozole (Arimidex®)

Last Modified: August 21, 2011

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Pronounced: an-AS-troe-zole
Classification: Aromatase Inhibitor

About Anastrozole

Anastrozole is an aromatase inhibitor, which works to decrease the overall levels of estrogen in a woman's body. In women who have gone through menopause, estrogen is mainly produced by converting androgens (sex hormones produced by the adrenal glands) into estrogens. An enzyme called aromatase is responsible for this conversion. Aromatase inhibitors block this conversion, leading to less estrogen in the body. While estrogen may not actually cause breast cancer, it is a necessary hormone for the cancer cells to grow in estrogen receptor-positive breast cancers. With estrogen blocked, the cancer cells that feed off estrogen may not be able to survive.

How to Take Anastrozole

Anastozole is taken in pill form, once daily. The drug may be taken with or without food.

Possible Side Effects of Anastrozole

There are a number of things you can do to manage the side effects of Anastrozole. Talk to your doctor or nurse about these recommendations. They can help you decide what will work best for you. These are some of the most common side effects:

Hot Flashes

There are a few things you can do to help with hot flashes. Several medications have been shown to help with symptoms, including clonidine (a blood pressure medication), low doses of certain antidepressants (such as venlafaxine and Prozac), and gabapentin. Non-medical recommendations include: keeping well-hydrated with eight glasses of water daily, wearing cotton or lightweight, breathable fabrics, dressing in layers, exercising on a regular basis (generally walking exercise is best), practicing relaxation exercises, and avoiding triggers such as warm rooms, spicy foods, caffeinated beverages, and alcohol.

Weakening of the Bones (Osteoporosis)

Your doctor will check your bone health before starting therapy. This is done with a bone density scan (dexa scan). Women with no weakening of bones prior to aromatase inhibitor therapy will have a follow-up scan around one year after starting therapy, and then every one to two years.

If the scan shows that you already have some bone weakening, your doctor may order a type of medication called a bisphosphonate or calcium and vitamin D supplements to help strengthen the bones. These therapies have been shown to protect the bones from bone loss in women taking aromatase inhibitors. If the bone density remains stable, scans can then be done every two years. Learn more about bone health after cancer therapy.

Muscle or Joint Pain/Aches and Headache

Aromatase inhibitor medications can cause joint or muscle aches and pains, which can interfere with quality of life. Be sure to talk to your oncology team if you develop this side effect. This pain is caused mainly by swelling in the joints, which is best treated by a non-steroidal anti-inflammatory (NSAID), such as ibuprofen, naprosen and celecoxib. Be sure to discuss which pain relievers you can safely take with your oncology team as these are not without their own side effects. Some studies have shown that acupuncture and gentle stretching and exercise may help reduce this pain. Learn more about AI related joint pain.


See OncoLink's section on fatigue for helpful tips on dealing with this side effect.

Vaginal Dryness

Vaginal dryness and related painful intercourse is one of the more common side effects of cancer therapy. Vaginal lubricants and moisturizers can help with these concerns. Learn more about specific recommendations for dealing with this side effect.

Other Side Effects

Chronic sore throat, hair thinning, rash and mood changes.

Fulvestrant Shows Benefits in Advanced Breast Cancer

Apr 1, 2015 - High-dose fulvestrant, an estrogen receptor antagonist, appears to be at least as effective as the aromatase inhibitor anastrozole as a first-line endocrine therapy in postmenopausal women with advanced hormone receptor-positive breast cancer, according to research published online Aug. 24 in the Journal of Clinical Oncology.

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