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How long do you need to take Aromasin?

Medically reviewed by Carmen Pope, BPharm. Last updated on March 15, 2023.

Official answer

  • Most women take Aromasin for two to three years.
  • Doctors may recommend some women take it for longer.
  • Aromasin is usually given after two to three years of treatment with tamoxifen, for a total of five years of continuous hormonal treatment.

Aromasin (exemestane) is a medication that is used to treat breast cancer in postmenopausal women. It is often given to women whose cancer has progressed despite surgery, radiation, or other cancer treatments.

The usual dosage is one 25mg tablet once daily after a meal. Most women take Aromasin for around two to three years. Doctors may recommend some women take it for longer.

Aromasin is usually given to women with estrogen-receptor positive early breast cancer who have already received two to three years of tamoxifen. The tamoxifen is stopped and the Aromasin is started to make up a total of five consecutive years of hormonal treatment.

  • Studies have shown that switching to Aromasin for two to three years AFTER taking tamoxifen is better than just staying on tamoxifen for five years.
  • Aromasin may also be given to women with advanced breast cancer whose disease has progressed following tamoxifen therapy.

How does Aromasin work?

Aromasin (exemestane) works by irreversibly inactivating an enzyme called aromatase. In postmenopausal women, the principal source of circulating estrogens comes from adrenal and ovarian androgens (such as androstenedione and testosterone) which aromatase converts into estrogens (such as estrone and estradiol).

Aromasin is structurally related to androstenedione, and the aromatase enzymes binds to it instead of binding to naturally occurring androstenedione. This irreversibly inactivates the enzyme, which reduces circulating levels of estrogens in the body.

Aromasin has no effect on adrenal biosynthesis or on other enzymes involved in the steroidogenic pathway so has no effects on the formation of corticosteroids, aldosterone, or any other enzyme.

Aromasin does not work on hormone-receptor negative breast cancer.

Aromasin is also not given to premenopausal women because it does not stop the ovaries from making estrogen. However, if women are willing to also take medication to suppress ovarian function, as well as effective nonhormonal birth control, then it may be given in certain circumstances.

What are the side effects of Aromasin?

Common side effects of Aromasin are:

  • Anxiety
  • Back pain
  • Bone and joint pain
  • Depression or low mood
  • Diarrhea
  • Dizziness
  • Dry skin
  • Hair changes
  • Headache
  • Heartburn or indigestion
  • High blood pressure
  • Hot flashes
  • Fatigue
  • Increased appetite
  • Increased sweating
  • Muscle and joint pain
  • Nausea
  • Sleeplessness
  • Swelling in the extremities (peripheral edema)
  • Visual disturbances.

Other side effects that may occur in less than 5% of women include:

  • Carpel tunnel syndrome
  • Diarrhea
  • Muscle cramps
  • Nerve pain
  • Osteoporosis or brittle bones.


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