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
Before you begin taking an aromatase inhibitor, talk with your health care team about possible side effects and how to manage them.
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 [130-131]. 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% have muscle pain [130-131].
Joint and muscle pain can mimic carpal tunnel syndrome. In rare cases, aromatase inhibitors can cause carpal tunnel syndrome [132-133].
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 [6,131,134-136]. Getting regular physical activity (such as walking, stretching or yoga) may reduce joint and muscle pain [6,131,136-137].
Your health care provider may also switch you to another aromatase inhibitor (you may have less pain with a different drug) or recommend tamoxifen [6].
Bone health
Aromatase inhibitors cause a loss of bone density, which leads to higher rates of osteoporosis and bone fractures compared to tamoxifen [11,130]. 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 before you begin treatment with an aromatase inhibitor. Future measures can be compared to this baseline measure to monitor any changes to your bone density.
Bone density is checked about every 2 years while taking an aromatase inhibitor.
Bone-strengthening therapy
Your health care provider may prescribe drugs called bisphosphonates or the drug denosumab to help maintain bone density while you’re taking an aromatase inhibitor [11]. These medications may help prevent osteoporosis.
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 [130,138]. This type of pain usually only lasts for 1-2 days, and only with the first treatment.
However, if you have any pain, report it to your health care provider right away.
In rare cases, osteonecrosis of the jaw, a serious jawbone disorder, may occur [139]. 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 and take care of any dental work before starting treatment with a bisphosphonate or denosumab [11].
Talk with your dentist before getting any dental work while you’re on bone-strengthening therapy and tell them you are on these medications. Routine dental cleanings are safe for people on bone-strengthening therapy.
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 [140].
For example, weight-bearing exercise helps protect bones and lowers the risk of hip fractures [141].
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 [142].
Menopausal symptoms
Watch our MBC Impact Series, Metastatic Breast Cancer and Sexual Health. Although this webinar was created for women who have metastatic breast cancer, it has helpful information on sexual health for women with any stage of breast cancer. We encourage all to watch.
Hot flashes and night sweats
Hot flashes and night sweats are common in women who take aromatase inhibitors [115].
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 team about ways to treat them.
Learn about treating hot flashes.
Vaginal dryness
Vaginal dryness is common in women who take aromatase inhibitors [115].
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 team 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 the table below).
Before you begin taking an aromatase inhibitor, talk with your health care team about possible side effects and how to manage them. Your provider can treat many of these side effects.
Side effects of aromatase inhibitors versus side effects of tamoxifen | ||
Aromatase inhibitors | Tamoxifen | |
Common side effects |
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Less common or rare side effects (Some of these side effects, including cancer of the uterus and stroke, are very rare.) |
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Adapted from select sources [11,100,115,118-121]. | ||
Learn more about the side effects of tamoxifen.
Learn more about side effects.
Long-term side effects of aromatase inhibitors
Even though aromatase inhibitors have been used for many years, more time is still needed to assess the long-term risks of these drugs.
Susan G. Komen® Support Resources |
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Updated 02/26/25
This content is regularly reviewed by an expert panel including researchers, practicing clinicians and patient advocates.
