Anastrozole (Arimidex®)

OncoLink Team
Last Modified: August 16, 2017

Pronounced: an-AS-troe-zole

Classification: aromatase inhibitor

About Anastrozole (Arimidex®)

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. Do not crush, break or chew the tablet. Your health care team will tell you how much medication you should take. If you miss a dose or vomit after taking your dose, do not take an additional dose. Wait to take your next dose at the scheduled time. Do not take two doses at the same time. Do not stop taking anastrozole without talking to your healthcare team.

It is important to make sure you are taking the correct amount of medication every time. Before every dose, check that what you are taking matches what you have been prescribed. If you take too much medication, notify your health care team or go to the emergency room immediately.

The blood levels of this medication can be affected by certain foods and medications, so they should be avoided. Be sure to tell your healthcare provider about all medications and supplements you take. 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 your medication in the original, labeled container at room temperature and in a dry location (unless otherwise directed by your healthcare provider or pharmacist). This medication should not be stored in a pillbox. Keep containers out of reach of children and pets.

If a caregiver prepares your dose for you, they should consider wearing gloves or pour the pills directly from their container into the cap, a small cup, or directly into your hand. They should avoid touching the pills. They should always wash their hands before and after giving you the medication. Pregnant or nursing women should not prepare the dose for you. 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.

Insurance Information

This medication may be covered under your prescription drug plan. Patient assistance may be available to qualifying individuals depending upon prescription drug coverage. Co-pay cards, which reduce the patient co-pay responsibility for eligible commercially (non-government sponsored) insured patients, may also be available. 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 care team about these recommendations. They can help you decide what will work best for you. These are some of the most common or important side effects:

Fatigue

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.

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 fluoxetine), and gabapentin. Talk to your healthcare team about these prescription products to determine if they are right for you.

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.

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 care 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 (Advil/Motrin), naproxen (Aleve) and celecoxib (Celebrex). 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.

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.

Nausea and/or Vomiting

Talk to your oncology care team 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 saltines, or ginger ale to lessen symptoms.

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

Diarrhea

Your oncology care team can recommend medications to relieve diarrhea. Also, try eating low-fiber, bland foods, such as white rice and boiled or baked chicken. Avoid raw fruits, vegetables, whole grain breads, cereals and seeds. Soluble fiber is found in some foods and absorbs fluid, which can help relieve diarrhea. Foods high in soluble fiber include: applesauce, bananas (ripe), canned fruit, orange sections, boiled potatoes, white rice, products made with white flour, oatmeal, cream of rice, cream of wheat, and farina. Drink 8-10 glasses on non-alcoholic, un-caffeinated fluid a day to prevent dehydration.

Weakening of the Bones (Osteoporosis) 

You may be advised to get plenty of calcium and vitamin D to reduce your risk of osteoporosis. It is best to get calcium in a balanced diet, including 4-8 servings of calcium rich foods a day.  Examples of calcium rich foods are low fat milk, yogurt, cheese, green leafy vegetables, nuts, seeds, beans, legumes and calcium fortified foods and juices. Vitamin D is not present in many foods, so it is harder to get in your diet. Our bodies make vitamin D when the sun hits our skin, but sun avoidance and sunblock prevent many from getting necessary amounts to support bone health. Your care team may recommend supplements of calcium and vitamin D and will tell you how much to take. Weight bearing exercise and strength exercises can also help protect your bone health.

Your provider 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. 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.

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.

Less common, but important side effects can include:

  • 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 will monitor for using blood tests called liver function tests. 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.

Reproductive Concerns

This medication should only be given to women who have gone through menopause. If you are unsure if you are in menopause or if you become pregnant while taking this medication, notify your care provider.


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