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Treatment Name: Anastrozole (Arimidex®)

Anastrozole (Arimidex®) is a Chemotherapy Regimen for Breast Cancer - metastatic

How does anastrozole work?
It is designed to inhibit an enzyme in your body called aromatase. Aromatase is responsible for helping produce estradiol (a type of estrogen). When anastrozole inhibits aromatase, there is almost no estrogen produced that would bind to the receptors on breast cancer cells to tell them to grow and divide. Patients with breast cancer that are not estrogen-receptor positive rarely respond to treatment with anastrozole.

Goals of therapy:
Anastrozole is commonly taken to slow the progression of the disease and prevent it from spreading further, not for cure.


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  • Usual starting dose: Anastrozole 1 mg oral tablet by mouth daily

Anastrozole is usually taken at home. Duration of therapy is until the cancer spreads or unacceptable side effects occur.

It is only indicated for use in post-menopausal women and should not be used by pre-menopausal women. Ask your doctor if you are unsure as to whether you are considered pre- or post-menopausal.

Side Effects

In clinical studies, the most commonly reported side effects with anastrozole are shown here. Side effects sometimes have percentage ranges [example: 13 – 31% experience nausea] because they differed between clinical studies:

A note about side effect percentages

  • Hot flashes (20 - 38%)
  • Joint pain (32%)
  • Fatigue (9 - 32%)
  • Nausea (13 - 31%)
  • Pain (8 - 25%)
  • Diarrhea (17%)
  • Bone pain (6%)
  • Fluid in extremities (6%)
  • Constipation (6%)
  • Sore throat (5%)
  • High blood pressure (5%)
  • Depression (5%)
  • Vaginal dryness (2 - 5%)
  • Weight gain (3%)
  • Stroke (2%)
  • Blood clots (1%)
  • Heart attack (1%)
  • Vaginal bleeding (1%)

Importantly, not all people who experience a side effect from Arimidex® (anastrozole) will experience it in the same way. It may be mild in some or severe in others, depending upon the individual. Everybody is different. Additionally, side effects may vary over time. For some, side effects may be a reason to delay or switch treatment, reduce the dose, or avoid future treatment with a certain medication altogether.

Side effects may be treatable when they occur or preventable by taking certain medications before they happen. When medications are taken to prevent a problem, this is known as prophylaxis, or "prophy" for short.

After starting treatment with Arimidex®, be sure to come back and watch all of the side effect videos shown below. Each of these videos contain valuable information about side effect management that will hopefully help you to both feel better and stay out of the hospital.

Side effect videos Side Effect Videos
PainPainDiarrheaDiarrheaNausea and VomitingNausea and VomitingFatigue Fatigue ConstipationConstipationBlood ClotsBlood Clots


How often is monitoring needed?
Labs (blood tests) may be checked every one to three months. Labs often include: Complete Blood Count (CBC), Comprehensive Metabolic Panel (CMP), triglycerides, and blood cholesterol levels.

How often is imaging needed?
Imaging may be checked before treatment and every two to six months during treatment. Imaging may include: bone scans, magnetic resonance imaging (MRI), and computerized tomography (CT) scans. DEXA (Dual-Energy X-ray Absorptiometry) scans may be performed to monitor your bone density.

How might blood test results/imaging affect treatment?
Depending upon the results, your doctor may advise to continue anastrozole as planned, or delay or switch therapy.

ChemoExperts Tips

  • Do not take estrogen replacement therapy or other medications that contain estrogen as they may decrease the effectiveness of anastrozole
  • Women with a history of heart disease may have an increased risk of heart attack with anastrozole compared with tamoxifen therapy. Your doctor will consider the risks and benefits of each therapy when deciding between treatments. Anastrozole and tamoxifen should NOT be taken together
  • A pharmacist should ALWAYS review your medication list to ensure that drug interactions are prevented or managed appropriately
  • Clinical trials may exist for breast cancer. Ask your doctor if any studies are currently enrolling in your area. If not, go to to search for other centers offering study medications

Patient Assistance & Co-payment Coverage

Patients under the age of 65 years, or those with private insurance plans:
If you have insurance and are looking for patient assistance or copay assistance for Anastrozole (Arimidex®), we have provided links that may help.

Visit our Patient Assistance page and click the links to various patient assistance programs for help paying for Anastrozole (Arimidex®). Depending upon your income, they may be able to help cover the cost of:

  • Anastrozole

For Branded medications (may be available for generic medications too), check with the manufacturer to determine if a co-pay card is offered and if it could reduce your monthly copay.

  • If you are uninsured, check with the manufacturer to determine if you are eligible to receive medication at no cost.

Medicare and Medicaid patients (Patients 65 years or older):
The clinic providing treatment will likely pre-authorize medications and immune therapies such as Anastrozole (Arimidex®) and are the best source to help you understand drug cost.

  • Ask to speak with a patient assistance technician or financial counselor at the clinic or hospital administering this therapy.

Emotional Wellness

What is Emotional Wellness?
Emotional wellness is having a positive outlook balanced with a realistic understanding of current life events. This requires both an awareness and acceptance of your emotions. It is with this knowledge that you can develop a plan to take the necessary actions to positively impact your life.

Emotional wellness uses an ongoing process to continually reflect on the stressors of life in a constructive manner to move forward and create happiness.

Because emotional wellness is deeply connected with physical, social, and spiritual wellness, pursuing it often becomes particularly difficult in times of major illness. Despite this difficulty, working toward emotional wellness has been connected to improved treatment outcomes and a higher likelihood of achieving goals of therapy.

Learn more about pursuing emotional wellness while receiving treatment with Anastrozole (Arimidex®)

Individual Drug Label Information

Anastrozole (Arimidex®)

  • Anastrozole is an oral tablet
  • Can be taken with or without food. Swallow tablets whole--do not crush
  • If you miss a dose, take it as soon as you remember if it’s the same day. If it is the next day, take your regular dose as scheduled. Do not double the dose to make up for the missed dose
  • Store at room temperature in a cool, dry place
  • Dosage adjustments may be required due to side effects
  • Notify your healthcare provider if you experience any tickling, tingling, or numbness
  • May cause fetal harm; avoid pregnancy
General Anastrozole (Arimidex) Side Effects
  • One of the most common side effects reported are hot flashes. Talk to your doctor about ways to minimize and treat hot flashes. Do not take any medicines, herbs, or natural supplements without speaking with your doctor or pharmacist first
  • Joint pain, back pain, general pain
  • Fatigue and weakness
  • Decreased bone strength and density, fractures
  • Increase in cholesterol in the blood
  • Nausea and vomiting
  • Increase risk of heart attack or chest pain in patients with a history of these problems
  • High blood pressure
  • Mood swings, depression, and insomnia
  • Headache
  • Fluid retention
  • Skin rash
  • Decreased sexual drive
  • Diarrhea or constipation
  • Click on the anastrozole (Arimidex) package insert below for reported side effects and possible drug interactions

Side Effect Videos
Nausea and VomitingNausea and VomitingDiarrheaDiarrheaFatigue Fatigue ConstipationConstipationPainPainBlood ClotsBlood Clots

See DailyMed package insert.

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1. Bonneterre J, Thurlimann B, Robertson J.F.Rr, et al. Anastrozole Versus Tamoxifen as First-Line Therapy for Advanced Breast Cancer in 668 Postmenopausal Women: Results of the Tamoxifen or Arimidex Randomized Group Efficacy and Tolerability Study. J Clin Oncol 2000;18:3748-3757.

2. Nabholtz JM, Buzdar A, Pollak M, et al. Anastrozole Is Superior to Tamoxifen as First-Line Therapy for Advanced Breast Cancer in Postmenopausal Women: Results of a North American Multicenter Randomized Trial. J Clin Oncol 2000;18:3758-3767.

Created: February 3, 2016 Updated: January 8, 2020

What is Breast Cancer - metastatic?

What is Metastatic Breast Cancer?
A disease of the milk-producing glands known as lobules, milk ducts, or other cells found in the breast. Metastatic breast cancer is one that has moved from the breast to other areas of the body, which may include the brain, liver, or bone. Breast cancer is one of the most common types of cancers in women, but may rarely affect men as well. Known causes of breast cancer include genetic causes, such as the BRCA mutation, or obesity. The effectiveness of the treatment may depend upon the stage at diagnosis.

Types of metastatic breast cancer:
1. Hormone-receptor positive or negative (60 - 65% of patients)

  • Estrogen Receptor positive (ER)+ or negative (ER)-
  • Progestin Receptor positive (PR)+ or negative (PR)-

2. Hormone Epidermal growth factor Receptor-2 (HER-2) positive or negative (20 - 25% of patients)

  • HER-2 +
  • HER-2 -

3. Triple Negative (15 - 18% of patients)

  • ER- and PR- and (HER-2)-
NOTE: Treatment Options listed below are not all-inclusive. Other treatments may be available. ChemoExperts provides drug information and does not recommend any one treatment over another. Only your Doctor can choose which therapy is appropriate for you.

Clinical Studies

If you are interested in reading the clinical trials results, please click on references below:

1. Bonneterre J, Thurlimann B, Robertson J.F.Rr, et al. Anastrozole Versus Tamoxifen as First-Line Therapy for Advanced Breast Cancer in 668 Postmenopausal Women: Results of the Tamoxifen or Arimidex Randomized Group Efficacy and Tolerability Study. J Clin Oncol 2000;18:3748-3757.

2. Nabholtz JM, Buzdar A, Pollak M, et al. Anastrozole Is Superior to Tamoxifen as First-Line Therapy for Advanced Breast Cancer in Postmenopausal Women: Results of a North American Multicenter Randomized Trial. J Clin Oncol 2000;18:3758-3767.

What is a CBC?

A Complete Blood Count (CBC) is a frequently ordered blood test that tells clinicians the status of your: 1) White blood cell count, 2) Hemoglobin, and 3) Platelet count at the time the test was taken.

Common uses:
1) White blood cell count (WBC): is used to determine infection risk, or response to chemotherapy. Certain chemotherapy agents may harm our good infection-fighting cells. Sometimes chemotherapy may need to be delayed to allow these cells to recover.

2) Hemoglobin: is used to determine if someone is anemic. Anytime the hemoglobin is below 12 g/dL, the person is said to be anemic. Red blood cell transfusions, and sometimes iron can be given to restore the hemoglobin level, but anemia treatment should always aim at treating the underlying cause or condition.

3) Platelet count: is used to determine if the risk of bleeding is increased or if a platelet transfusion is required to prevent bleeding. Certain medications that increase bleeding risk, such as: aspirin, certain chemotherapy agents, and blood thinners, may need to be stopped temporarily until the platelet count is within a safe range.

What is a CMP?

A Comprehensive Metabolic Panel (CMP) is a frequently ordered blood test that tells clinicians the status of your: 1) Electrolytes & Acid/Base status2) Kidney function, 3) Liver function, 4) Blood sugar, and 5) Calcium at the time the test was taken. It is commonly used to monitor liver and kidney function when beginning new medications such as chemotherapy. A total of 14 tests are run simultaneously and are shown below.

Electrolytes & Acid/Base status:
1) Sodium, 2) Potassium, 3) Carbon dioxide, 4) Chloride

Kidney Function:
5) BUN (blood urea nitrogen), 6) Serum creatinine (Scr)

Liver Function:
7) AST, 8) ALT, 9) Total bilirubin, 10) Alk Phos, 11) Albumin, 12) Total protein

Blood sugar:
13) Serum glucose

14) Serum calcium

What does Cure mean?

The word “cure” means there are no cancer cells left in the body and cancer will never come back. Depending on the cancer type and stage, this may be the true goal of therapy. However, it is very difficult to prove all cancer cells are gone. Even though images, like X-rays and MRI’s, and blood tests may not show any signs of cancer, there can be a small amount of cancer cells still left in the body. Because of this, the word “remission” is used more often. This means there are no signs or symptoms of cancer. Patients in remission are followed closely for any signs of cancer returning. Sometimes, more chemotherapy may be given while in remission to prevent the cancer from coming back.

Doctors usually do not consider a patient “cured” until the chance of cancer returning is extremely low. If cancer does return, it usually happens within 5 years of having a remission. Because of this, doctors do not consider a patient cured unless the cancer has not come back within 5 years of remission. The five-year cutoff does not apply to all cancers.

A note about side effect percentages

The number you see next to the percent sign (%) means how many people out of 100 are likely to experience this side effect.

For example, if the side effect is reported to occur in 8% of patients, this means that roughly 8 out of 100 people receiving this treatment will experience this side effect.