Exemestane

Say it: ex-eh-MES-tane · Brand names: Aromasin

Exemestane is a hormone therapy pill called an aromatase inhibitor that lowers the amount of estrogen in the body.

What it is

After menopause, the body still makes some estrogen using an enzyme called aromatase. Exemestane attaches to this enzyme and stops it from working, so the body makes much less estrogen. Breast cancers that need estrogen to grow then slow down or stop.

Often used for

• hormone receptor positive early breast cancer after menopause, after 2 to 3 years of tamoxifen
• hormone receptor positive breast cancer after menopause that has grown after tamoxifen
• breast cancer that has spread, given with everolimus

How you get it

Exemestane is a pill you take by mouth at home, once a day after a meal. Your schedule may be different.

Common side effects and what helps

• Hot flashes or night sweats. Dress in layers, keep your room cool, and limit caffeine and alcohol.
• Feeling tired or weak. Rest when you need to, and try short walks.
• Joint or muscle aches and stiffness. Regular gentle exercise often helps.
• Headache. Ask your team which pain medicines are safe.
• Trouble sleeping. Keep a regular bedtime and limit caffeine.
• More sweating. Wear light, breathable clothing.
• Feeling sick to your stomach or throwing up. Eat small meals and ask your team about anti-nausea medicine.
• Hair thinning. Use a gentle shampoo.

Call your care team right away if you have

• Chest pain or pressure, or a racing or pounding heartbeat
• Sudden weakness or numbness of the face, arm, or leg, or trouble speaking
• Swelling, pain, or warmth in one leg, or sudden shortness of breath
• Bone pain that is new or very bad, or a broken bone

Before you start, tell your team

• If you are pregnant, may become pregnant, or are breastfeeding
• If you have not gone through menopause
• If you have bone thinning (osteoporosis)
• If you have liver or kidney problems
• If you take any medicine or supplement with estrogen, since it can stop this medicine from working

Good to know

• It can thin your bones over time. You may have bone density scans, and your team may suggest calcium, vitamin D, or other medicines.
• Your team may check your vitamin D level before you start.

At home

• Take the tablet at about the same time each day, after a meal.
• If you miss a dose or throw up after taking it, ask your team what to do. Do not take extra pills to make up for it.
• Store the pills at room temperature in the original bottle, away from children and pets.

Questions to ask

• How long will I take this medicine?
• Do I need a bone density scan?
• What can I do about joint aches?
• What can I do about hot flashes?

Side effect guides

• Fatigue (tiredness)
• Nausea and vomiting
• Hair loss
• Sleep problems
• Pain

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.