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Side Effects of Aromatase Inhibitors

Aromatase inhibitors are hormone therapy drugs used to treat hormone receptor-positive breast cancer. They include:

  • Anastrozole (Arimidex)
  • Exemestane (Aromasin)
  • Letrozole (Femara)

Aromatase inhibitors are used to treat breast cancers in:

  • Postmenopausal women
  • Premenopausal women who also get ovarian suppression

Some common side effects are described below.   

Joint and muscle pain

Joint pain (arthralgia) and muscle pain (myalgia) are common side effects of aromatase inhibitors [115-116]. The pain may be in the hands and wrists, feet and ankles, knees, back or other parts of the body. Joint and muscle pain are most common after you’ve been sleeping or inactive.

Almost half of women taking aromatase inhibitors have joint pain and about 15 percent have muscle pain [115-116].

Joint and muscle pain can mimic carpal tunnel syndrome. In rare cases, aromatase inhibitors can cause carpal tunnel syndrome [117].

Although aromatase inhibitors can cause joint and muscle pain, they don’t cause permanent joint or muscle damage.

Easing joint or muscle pain

If you have joint or muscle pain while taking an aromatase inhibitor, talk with your health care provider.

Your health care provider may recommend anti-inflammatory medications (such as aspirin or ibuprofen), special exercises or acupuncture to ease the pain [116,118]. Getting regular physical activity (such as walking, stretching or yoga) may reduce joint and muscle pain [119-120].

Your health care provider may also switch you to another aromatase inhibitor (you may have less pain with a different drug) or recommend tamoxifen [121].

Bone health

Aromatase inhibitors cause a loss of bone density, which leads to higher rates of osteoporosis and bone fractures compared to tamoxifen [8,115]. Osteoporosis is a loss of bone mass and bone density. It causes bones to become fragile.

Monitoring bone health

Your health care provider will take a baseline measure of your bone density. Future measures can be compared to this baseline measure to monitor changes to your bone density.

Bone-strengthening therapy

Some medications may help prevent osteoporosis while you are taking an aromatase inhibitor. 

Your health care provider may prescribe drugs called bisphosphonates or the drug denosumab to help maintain bone density.

Health risks of bisphosphonates and denosumab

Although mostly a concern for people with metastatic breast cancer who get higher doses of bisphosphonates or denosumab, these drugs can cause bone, joint and muscle pain [115,122]. This type of pain usually only last for 1-2 days, and only with the first treatment.

However, if you have any of these symptoms, report them to your health care provider right away.

In rare cases, osteonecrosis of the jaw, a serious jawbone disorder, may occur [123-124]. This is mostly a concern for people with metastatic breast cancer who take frequent doses of bisphosphonates for long periods of time.

It’s recommended you have a dental exam (along with any dental work that needs to be done) before you start treatment with a bisphosphonate or denosumab [8,123]. Before getting any dental procedure while on bone-strengthening therapy, talk with your oncologist [8,123]. Also, tell your dentist you are on one of these medications.

Learn more about bisphosphonates and breast cancer treatment.

Exercise, diet and not smoking

Weight-bearing exercise (exercise that involves standing rather than sitting, such as walking and dancing) and resistance training (such as lifting weights and lunges) can help strengthen and protect your bones [125].

For example, weight-bearing exercise helps protect bones and lowers the risk of hip fractures [126].

Getting enough calcium and vitamin D (your health care provider can tell you if you’re getting enough) and not smoking can also help strengthen your bones [127].

Menopausal symptoms

Hot flashes and night sweats

Hot flashes and night sweats are common in women who take aromatase inhibitors [102].

Although these symptoms may become less frequent and less intense over time, they can still be hard to manage.

If the hot flashes bother you, talk with your health care provider about ways to treat them.

Learn about treating hot flashes.

Vaginal dryness

Vaginal dryness is common in women who take aromatase inhibitors [102].

Unlike hot flashes, vaginal symptoms tend to become worse over time.

If you have vaginal dryness or other vaginal symptoms, talk with your health care provider about ways to treat them.

Learn about treating vaginal symptoms.

Side effects of aromatase inhibitors versus side effects of tamoxifen

Although both aromatase inhibitors and tamoxifen can cause menopausal symptoms such as hot flashes, many of their side effects differ (see Figure 5.11 below).

Your health care provider can treat many of these side effects.    

Figure 5.11: Side effects of aromatase inhibitors versus side effects of tamoxifen


Aromatase inhibitors


Common side effects

  • Hot flashes and night sweats
  • Joint and muscle pain
  • Loss of bone mineral density (may lead to osteoporosis or bone fractures)
  • Loss of sex drive
  • Vaginal dryness or itching
  • Hot flashes and night sweats
  • Loss of sex drive
  • Vaginal discharge
  • Vaginal dryness or itching

Less common or rare side effects

(Some of these side effects, including cancer of the uterus and stroke, are very rare.)

  • Carpal tunnel syndrome
  • Hair thinning
  • Heart problems
  • Increased blood pressure
  • Increased cholesterol
  • Mood swings and depression
  • Blood clots in the large veins (deep vein thrombosis)
  • Blood clots in the lungs (pulmonary emboli)
  • Bone loss (premenopausal women only)
  • Cancer of the uterus (uterine or endometrial cancer)
  • Cataracts
  • Stroke
  • Vaginal bleeding

Adapted from select sources [8,91,102,105-108].

Learn more about the side effects of tamoxifen.

Long-term side effects of aromatase inhibitors

Even though aromatase inhibitors have been used for a while, more time is still needed to assess the long-term risks of these drugs.


  • If you or a loved one needs more information about breast health or breast cancer, contact the Komen Breast Care Helpline at 1-877 GO KOMEN (1-877-465-6636) or email helpline@komen.org. All calls are answered by a trained specialist or oncology social worker, Monday through Friday from 9:00 a.m. to 10:00 p.m. ET. Se habla español.
  • Komen Patient Navigators can help guide you through the health care system as you go through a breast cancer diagnosis. They can help to remove barriers to high-quality breast care. For example, they can help you with insurance, local resources, communication with health care providers and more. Call the Komen Breast Care Helpline at 1-877 GO KOMEN (1-877-465-6636) or email helpline@komen.org to learn more about our Patient Navigator program, including eligibility.
  • Komen Facebook groups provide a place where those with a connection to breast cancer can share their experiences and build strong relationships with each other. Visit Facebook and search for “Komen Breast Cancer group” or “Komen Metastatic Breast Cancer group” to request to join one of our closed groups.
  • Our fact sheets, booklets and other education materials offer additional information.

 Updated 05/27/22