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Aromasin - Breast Cancer Adjuvant Hormone Therapy


Updated June 29, 2008

Aromasin pills

Aromasin pills

Karl D. Stephan


Aromasin (exemestane) is an antiestrogen, or estrogen suppressor medication, taken as a 25 mg pill. Aromasin is a steroid. This medication helps lower your risk of breast cancer recurrence, and improves your chance of survival.

Drug type:

The enzyme aromatase is present in fat tissues, such as breast tissue. Aromasin inhibits this aromatase, which converts pre-estrogen to active estrogen. This is how Aromasin suppresses estrogen levels after adjuvant chemotherapy treatment for estrogen receptor-positive breast cancer and in women with advanced (metastatic) disease.


Aromasin is given to female breast cancer patients to lower estrogen levels and prevent recurrence of breast cancer. Patients who take Aromasin must be post-menopausal, have finished primary treatment for estrogen receptor-positive breast cancer, and have already taken two or three years of tamoxifen. This drug is also given to patients with advanced breast cancer, when tamoxifen has not halted the spread of cancer.



Also known as:

exemestane tablets

Available as:

brand name pills, no generic version available, by prescription only

Common Misspelling:



Take Aromasin once a day with a meal. Try to take it at the same time each day, to maintain the drug at an even level in your system. If you miss a dose, don’t double up, just wait till the next day and resume your medication schedule. Do not take this drug if you are still having menstrual periods, or are pregnant. Ask your doctor if this drug will conflict with any other medications that you take regularly.

How Aromasin Works:

Many breast tumors are fueled by estrogen. Aromasin and tamoxifen are drugs that target estrogen, but work by different methods. Before menopause, your ovaries produce most of your estrogen. After menopause, the ovaries stop making estrogen, but your breast and fatty tissues use the enzyme aromatase to continue making this hormone. Aromasin blocks aromatase, preventing estrogen production and lowering your hormone levels up to 98 percent. If breast cancer cells are present in your system, they have much less chance to grow if they can’t get any estrogen.

Common Side Effects:

Aromasin may cause these side effects:
  • hot flashes
  • headaches
  • fatigue
  • joint pain
  • insomnia
  • increased perspiration
Less common side effects (under five percent):
  • osteoporosis (bone thinning)
  • nausea
  • increased appetite
  • chest pain or discomfort
  • heart failure


The temporary side effects of Aromasin are much more tolerable when you know that your risk of recurrence is greatly reduced. Women who switched to Aromasin after two or three years of tamoxifen had significantly lower risk of recurrence that those who took a full five years of tamoxifen. In addition, with Aromasin your risk of a new cancer in the opposite breast is less than with tamoxifen alone.

Pfizer Oncology. Our Cancer Products, Aromasin® (exemestane tablets). Aromasin®

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