Arimidex – Anastrozole – Aromatase Inhibitor for Breast Cancer

Arimidex - Anastrozole Tablets
Arimidex - Anastrozole Tablets. Photo © Gold Standard

Arimidex and tamoxifen are both given to treat estrogen receptor-positive breast cancer. Women who are postmenopausal can take Arimidex to deplete circulating levels of estrogen, and help prevent a recurrence of breast cancer. For women who are pre-menopausal, tamoxifen is preferred because Arimidex may cause painful and potential dangerous cysts in the ovaries.

Definition of Arimidex:

Arimidex is an aromatase inhibitor that helps prevent the production of estrogen, a hormone that fuels many breast cancer tumors.

Aromatase inhibitors block the enzyme aromatase, a substance that helps your body tissues produce estrogen. Arimidex is considered a hormonal treatment, and can help prevent recurrence (return) of breast cancer. This drug is not a steroid.

Use for Breast Cancer:

Arimidex is used for all forms and stages of estrogen receptor positive breast cancer. If you have Triple Negative or estrogen receptor negative breast cancer, this drug will not benefit you.

Also known as:


How Arimidex Works:

Many breast tumors are fueled by estrogen. Before menopause, your ovaries produce most of your estrogen. After menopause, the ovaries stop making estrogen, but your adrenal glands, breast, and fatty tissues use the enzyme aromatase to continue making this hormone. Arimidex binds to aromatase, preventing estrogen production and lowering your overall hormone levels. If breast cancer cells are present in your system, they have much less chance to grow if they can’t get any estrogen.

This therapy is aimed at preventing a risk of breast cancer recurrence.

How to take Arimidex:

Arimidex is taken as a once-daily tablet. Take it at the same time each day with a drink of water. Do not chew or crush the tablet. You can take this drug with or without food. If you forget to take a dose, wait until the following day and resume taking the drug on schedule.

Possible side effects of Arimidex:

Arimidex is well-tolerated, and half of all women using this drug do not experience any side effects. You may not experience all of these side effects, but patients with early stage breast cancer have reported these symptoms:

  • hot flashes
  • joint pain
  • weakness
  • mood swings
  • sore throat
  • nausea and vomiting
  • depression
  • high blood pressure
  • osteoporosis (bone thinning)
  • swelling of arms and/or legs
  • headache

Call Your Doctor If You Have This Symptom:

  • persistent vomiting

Increased Risk of Bone Fractures:

Arimidex keeps your estrogen levels very low. With Arimidex, you are at 10% risk for fractures of spine, hip, and wrist (compared to a 7% risk on tamoxifen). Your bones need a certain amount of estrogen to keep them strong. But if you're taking Arimidex, you will need to be more careful about the risk of bone fracture if you fall or are in an accident. Be sure to ask your doctor what precautions you should take for your bone health, such as taking vitamin D and calcium supplements.

Who Should Avoid Arimidex:

  • Arimidex could harm an unborn child, so don't take this drug if you are pregnant.
  • If you are breastfeeding, avoid Arimidex because it may leach into your breast milk.
  • If you are currently taking tamoxifen, don't take Arimidex as well. Tamoxifen is actually a weak estrogen, and would conflict with Arimidex.
  • Women who had estrogen-receptor negative breast cancer will not benefit from Arimidex.

Recommendations during treatment:

  • Use contraception, if there is any chance that you could become pregnant
  • Try to reduce your stress levels -– a common hot flash trigger
  • Take ibuprofen for joint pain, or try soaking in a hot bath or taking a hot shower
  • If you have persistent nausea and vomiting, talk to your doctor and see what adjustments can be made to help you regain your appetite and avoid further problems
  • For good bone health, do weight-bearing exercise, avoid alcohol and tobacco, and eat a healthy diet that includes calcium and vitamin D.


    Drugs@FDA. Arimidex Label and Approval History. 9/16/2005.

    Continue Reading