Exemestane (Aromasin®)

Last Modified: August 21, 2011

Pronounced: ex-e-MES-tane
Classification: Aromatase Inhibitor

About Exemestane

Exemestane is an aromatase inactivator, which works to decrease the overall levels of estrogen in a woman's body. In women who have gone through menopause, estrogen is mainly produced by the aromatase enzyme, which converts androgens (sex hormones produced by the adrenal glands) into estrogens. Exemestane binds to aromatase, changing the protein permanently. This change "turns off" aromatase so that it can no longer make estrogen. While estrogen may not actually cause breast cancer, it is necessary for the cancer to grow in certain breast cancers. With estrogen blocked, the cancer cells that feed off estrogen may not be able to survive.

How to Take Exemestane

Exemestane comes as a tablet to take by mouth. It should be taken once a day after a meal. Take exemestane at around the same time every day.

Possible Side Effects of Exemestane

There are a number of things you can do to manage the side effects of Exemestane. Talk to your doctor or nurse about these recommendations. They can help you decide what will work best for you. These are some of the most common side effects:

Hot Flashes

There are a few things you can do to help with hot flashes. Several medications have been studied, including clonidine (a blood pressure medication), some low dose antidepressants (such as venlafaxine and Prozac), and gabapentin. Non-medical recommendations include: keeping well-hydrated with eight glasses of water daily, wearing cotton or lightweight, breathable fabrics, dressing in layers, exercising on a regular basis (generally walking exercise is best), practicing relaxation exercises, and avoiding triggers such as warm rooms, spicy foods, caffeinated beverages, and alcohol.

Weakening of the Bones (Osteoporosis)

Your doctor will check your bone health before starting therapy. This is done with a bone density scan (dexa scan). Women with no weakening of bones prior to aromatase inhibitor therapy will have a follow-up scan around one year after starting therapy, and then every one to two years.

If the scan shows that you already have some bone weakening, your doctor may order a type of medication called a bisphosphonate to help strengthen the bones. Your doctor may order this along with calcium supplements, depending on your situation. This type of therapy has been shown to protect the bones from bone loss in women taking aromatase inhibitors. If the bone density remains stable, scans can then be done every two years. Learn more about bone health after cancer therapy.

Muscle or Joint Pain/Aches and Headache

Aromatase inhibitor medications can cause joint or muscle aches and pains, which can interfere with quality of life. Be sure to talk to your oncology team if you develop this side effect. This pain is caused mainly by swelling in the joints, which is best treated by a non-steroidal anti-inflammatory (NSAID), such as ibuprofen, naproxen and celecoxib. Be sure to discuss which pain relievers you can safely take with your oncology team, as these are not without their own side effects. Some studies have shown that acupuncture and gentle stretching and exercise may help reduce this pain. Learn more about AI related joint pain.


While on cancer treatment you may need to adjust your schedule to manage fatigue. Plan times to rest during the day and conserve energy for more important activities. Exercise can help combat fatigue; a simple daily walk with a friend can help. Talk to your healthcare team and see OncoLink's section on fatigue for helpful tips on dealing with this side effect.

Vaginal Dryness

Vaginal dryness and related painful intercourse is one of the more common side effects of cancer therapy. Vaginal lubricants and moisturizers can help with these concerns. Learn more about specific recommendations for dealing with this side effect.


Insomnia was reported in clinical trials of exemestane. See OncoLink's section on insomnia for helpful tips.