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Anastrozole (Arimidex®)

OncoLink Team
Last Modified: July 20, 2015

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

Anastrozole is a tablet that is taken by mouth. You can take this medication with or without food. Your health care team will tell you how much medication you should take. If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose. Do not take two dosses at the same time.  Do not stop taking anastrozole without talking to your healthcare team. If you take too much medication, notify your health care team or go to the emergency room immediately.

Be sure to tell your healthcare team about all medications you take before starting anastrozole, including over the counter medications, vitamins and herbal supplements. You should not take this medication if you are currently taking tamoxifen, or other medications that include estrogen, including hormone replacement therapy, birth control pills, estrogen creams, vaginal ring and vaginal suppositories.

Storage and Handling

Store this medication at room temperature in the original container. If you prefer to use a pillbox, discuss this with your oncology pharmacist.  Ask your oncology team where to return any unused medication for disposal. Do not flush down the toilet or throw in the trash.

Where do I get this medication?

Anastrozole is available through your local retail/mail order pharmacy.  Your oncology team can work with your prescription drug plan to identify an in-network retail/mail order pharmacy for medication distribution. In some cases, mail order may be less expensive.

Insurance Information

This medication may be covered under your prescription drug plan. Patient assistance may be available to qualifying individuals without prescription drug coverage or for those with Medicare part D. Your care team can help you find these resources, if they are available.

Possible Side Effects

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:

  • Keep well-hydrated with eight glasses of water daily.
  • Drink ice water or apply an ice pack at the onset of a hot flash.
  • Wear cotton or lightweight, breathable fabrics and dress in layers so you can adjust as needed.
  • Exercise on a regular basis.
  • Try practicing meditation or relaxation exercises to manage stress, which can be a trigger.
  • Avoid 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. In addition, weight bearing exercise and a healthy diet rich in calcium and vitamin D can help protect bone health.

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. Studies have shown that acupuncture and gentle stretching and exercise may also help reduce this pain.

Increased Blood Cholesterol

Anastrozole can cause an increase in your cholesterol levels. Your healthcare team will monitor your cholesterol levels throughout you treatment.   

Heart Problems

This medication may increase symptoms of decreased blood flow to the heart in women who have a history of a blockage in their arteries. If you experience new or worsening chest pain or shortness of breath go to the emergency room immediately.

Liver Toxicity

This medication can cause liver toxicity, which your doctor may monitor for using blood tests called liver function tests. If you develop elevations in your liver function tests, your healthcare provider may need to lower your dose or stop the medication. Notify your healthcare provider if you notice yellowing of the skin or eyes, your urine appears dark or brown or pain in your abdomen, as these can be signs of liver toxicity.


Fatigue is very common during cancer treatment and is an overwhelming feeling of exhaustion that is not usually relieved by rest. While on cancer treatment, and for a period after, you may need to adjust your schedule to manage fatigue. Plan times to rest during the day and conserve energy for more important activities. Exercise can help combat fatigue; a simple daily walk with a friend can help.  Talk to your healthcare team for helpful tips on dealing with this side effect.

Nausea and/or Vomiting

Talk to your doctor or nurse so they can prescribe medications to help you manage nausea and vomiting. In addition, dietary changes may help. Avoid things that may worsen the symptoms, such as heavy or greasy/fatty, spicy or acidic foods (lemons, tomatoes, oranges). Try antacids, (e.g. milk of magnesia, calcium tablets such as Tums), saltines, or ginger ale to lessen symptoms.

Call your doctor or nurse if you are unable to keep fluids down for more than 12 hours or if you feel lightheaded or dizzy at any time.

Vaginal Dryness

Vaginal dryness and related painful intercourse is one of the more common side effects of cancer therapy in women. Vaginal lubricants and moisturizers (longer lasting form of moisturizers) can help with these concerns. Talk to your healthcare team for more suggestions in managing this side effect.

Mood Changes

Some women report mood swings and depression while on hormone therapy. It can be helpful to talk about concerns and feelings with a partner or close friend. If you find that feelings of sadness are interfering with life, talk with your team about finding a counselor experienced in working with cancer patients.

Reproductive Concerns

Exposure of an unborn child to this medication could cause birth defects, so you should not become pregnant or father a child while on this medication. Effective birth control is necessary during treatment. Even if your menstrual cycle stops or you believe you are not producing sperm, you could still be fertile and conceive.  You should consult with your healthcare team before breastfeeding while receiving this medication.


If you have questions or concerns about the medication that you have been prescribed, please contact your healthcare team. OncoLink is designed for educational purposes only and is not engaged in rendering medical advice or professional services. The information provided through OncoLink should not be used for diagnosing or treating a health problem or a disease. It is not a substitute for professional care. If you have or suspect you may have a health problem, you should consult your health care provider.


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