What Are Aromatase Inhibitors and How Do They Work?

Aromatase inhibitors (AIs) are medicines that lower the amount of estrogen in the body for some women. They work by blocking an enzyme called aromatase that turns other hormones into estrogen in fat tissue.

Who Should Take Aromatase Inhibitors?

These drugs mainly help women who:

  • Have gone through menopause
  • Have a type of breast cancer fueled by estrogen
  • Are at high risk for breast cancer

AIs don’t stop the ovaries from making estrogen. They only work to lower estrogen levels in women whose ovaries have stopped releasing hormones after menopause.

Approved Aromatase Inhibitor Drugs

Two AIs that research shows can lower breast cancer risk in postmenopausal women are:

  • Anastrozole – Brand name Arimidex
  • Exemestane – Brand name Aromasin

Doctors more often prescribe these drugs to treat hormone receptor-positive breast cancer rather than to reduce breast cancer risk.

If used to lower breast cancer risk, they are typically taken daily for 5 years.

Can Aromatase Inhibitors Reduce Breast Cancer Risk?

Studies have found that anastrozole and exemestane can lower the chance of postmenopausal women at increased risk getting breast cancer.

While not FDA approved for lowering breast cancer risk, expert groups list AIs as options for reducing risk in postmenopausal women along with other drugs like tamoxifen and raloxifene. For example, they may be a good choice for women at risk of blood clots, since blood clots are a side effect of tamoxifen and raloxifene.

What Are Some Side Effects of Aromatase Inhibitors?

Some common side effects of AIs are:

  • Menopause symptoms – hot flashes, night sweats, vaginal dryness
  • Muscle/joint pain – can be serious enough to stop taking the drug
  • Weakening bones/osteoporosis – higher chance of breaking bones
  • Raised cholesterol – potentially increasing heart problems

Doctors may check your bone density before prescribing AIs since they can speed up bone loss over time.

Let your doctor know if side effects become too difficult to manage when taking an aromatase inhibitor drug. There may be ways to help relieve symptoms or alternative options to discuss.

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Aromatase Inhibitors