Anastrozole
Say it: an-AS-troh-zole · Brand names: Arimidex
Anastrozole 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. Anastrozole blocks this enzyme 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, to lower the chance it comes back
- hormone receptor positive breast cancer after menopause that is advanced or has spread
How you get it
Anastrozole is a pill you take by mouth at home, once a day, with or without food. It is often taken for 5 years or longer. 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.
- Joint or muscle aches and stiffness. Regular gentle exercise often helps.
- Feeling weak or tired. Rest when you need to and try short walks.
- Mood changes. Talk with your team if you feel down.
- Feeling sick to your stomach or throwing up. Eat small meals and ask your team about anti-nausea medicine.
- Rash. Use gentle soap and fragrance free lotion.
- Thinning bones. Ask your team about calcium, vitamin D, and exercise.
- Headache or sore throat. Ask your team which medicines are safe.
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
- A rash with blisters, peeling skin, or sores in your mouth or eyes
- Swelling of your face, lips, or throat, or trouble breathing
- Yellow skin or eyes, dark tea colored urine, or pain on the right side of your belly
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 heart disease
- If you have bone thinning (osteoporosis) or high cholesterol
- If you take tamoxifen
- 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.
- People who already have heart disease may have a higher chance of heart problems. Tell your team about your heart history.
- Your cholesterol may be checked.
At home
- Take the tablet at about the same time each day.
- 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
Sources
Quick answers
- What is Anastrozole?
- Anastrozole is a hormone therapy pill called an aromatase inhibitor that lowers the amount of estrogen in the body. Brand names: Arimidex.
- What is Anastrozole used for?
- hormone receptor positive early breast cancer after menopause, to lower the chance it comes back; hormone receptor positive breast cancer after menopause that is advanced or has spread.
- How is Anastrozole given?
- Anastrozole is a pill you take by mouth at home, once a day, with or without food. It is often taken for 5 years or longer. Your schedule may be different.
- What are the common side effects of Anastrozole?
- Hot flashes or night sweats. Joint or muscle aches and stiffness. Feeling weak or tired. Mood changes. Feeling sick to your stomach or throwing up. Rash. Thinning bones. Headache or sore throat.
- When should I call my care team while taking Anastrozole?
- Chest pain or pressure, or a racing or pounding heartbeat; Sudden weakness or numbness of the face, arm, or leg, or trouble speaking; A rash with blisters, peeling skin, or sores in your mouth or eyes; Swelling of your face, lips, or throat, or trouble breathing; Yellow skin or eyes, dark tea colored urine, or pain on the right side of your belly.
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.