Generic name: anastrozole [ an-AS-troe-zole ]
Drug classes: Aromatase inhibitors, Hormones / antineoplastics

Medically reviewed by Melisa Puckey, BPharm. Last updated on Mar 1, 2024.

What is Arimidex?

Arimidex lowers estrogen levels in postmenopausal women, which may slow the growth of certain types of breast tumors that need estrogen to grow in the body.

Arimidex is used to treat breast cancer in postmenopausal women.

Arimidex is often given to women whose cancer has progressed even after taking tamoxifen (Nolvadex, Soltamox).

Warnings

Arimidex may decrease blood flow to your heart, especially if you have ever had coronary artery disease (clogged arteries). Seek medical attention if you have new or worsening chest pain, or if you feel short of breath.

Do not use anastrozole if you are pregnant. It could harm the unborn baby.

Arimidex may not work as well if you take it together with estrogen medication (such as hormone replacement therapy, estrogen creams, or birth control pills, injections, implants, skin patches, and vaginal rings).

Arimidex may increase your risk of a stroke or blood clot. Call your doctor at once if you have sudden numbness or weakness, (especially on one side of the body), sudden severe headache, slurred speech, or problems with vision or balance.

Before taking this medicine

You should not use Arimidex if you are allergic to anastrozole, or if you have not yet completed menopause.

Arimidex is not approved for use in men or children.

You should not take anastrozole if you also take tamoxifen.

To make sure this medicine is safe for you, tell your doctor if you have ever had:

• heart problems;

• coronary artery disease (clogged artery disease);

• high cholesterol; or

• osteoporosis or low bone mineral density.

Hormonal cancer treatment can weaken your bones. You may be more likely to have a broken bone while using Arimidex. Talk with your doctor about ways to keep your bones healthy.

Although it is not likely that a postmenopausal woman would be pregnant, anastrozole may harm an unborn baby. You may need to have a negative pregnancy test before starting this treatment. Use effective birth control if you are not past menopause. Keep using birth control for at least 3 weeks after your last dose of Arimidex. Tell your doctor if you become pregnant.

Do not breastfeed while using this medicine, and for at least 2 weeks after your last dose.

Related/similar drugs

Verzenio, Ibrance, tamoxifen, anastrozole, Xeloda, Femara, Herceptin

How should I take Arimidex?

Take Arimidex exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

Arimidex is usually taken once per day. Follow your doctor's dosing instructions very carefully.

You may take Arimidex with or without food.

You may need to keep taking this medication for up to 5 years. Follow your doctor's instructions.

Store at room temperature away from moisture and heat.

Dosing information

Usual Adult Dose for Breast Cancer:

Initial dose: 1 mg orally taken once a day
Duration of therapy: Until tumor progression (treatment of advanced breast cancer); unknown (adjuvant treatment of early breast cancer)

Uses:
-Adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer;
-First-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor unknown locally advanced or metastatic breast cancer;
-Second-line treatment of advanced breast cancer in postmenopausal women with disease progression following tamoxifen therapy.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What to avoid

Avoid driving or hazardous activity until you know how this medicine will affect you. Your reactions could be impaired.

Arimidex side effects

Get emergency medical help if you have signs of an allergic reaction to Arimidex (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Anastrozole may decrease blood flow to your heart, especially if you have ever had coronary artery disease (clogged arteries). Seek medical attention if you have new or worsening chest pain, or if you feel short of breath.

Call your doctor at once if you have:

• shortness of breath (even with mild exertion), swelling, rapid weight gain;

• numbness, prickly feeling, pain, or weakness in your hands or wrists;

• symptoms of bone fracture - bruising, swelling, tenderness, pain that worsens with movement;

• liver problems - right-sided upper stomach pain, yellowing of your skin or eyes, and not feeling well; or

• signs of a stroke - sudden numbness or weakness (especially on one side of the body), sudden severe headache, slurred speech, problems with vision or balance.

Common Arimidex side effects may include:

• numbness, tingling, or tickling feeling in your skin;

• hot flashes;

• weakness;

• joint pain or stiffness;

• bone pain, risk of fracture;

• swelling in your arms, legs, or feet;

• sore throat, cough, shortness of breath;

• headache, back pain;

• depression, sleep problems (insomnia);

• high blood pressure;

• nausea, vomiting; or

• rash.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Arimidex?

Arimidex may not work as well if you take it together with an estrogen medication (such as hormone replacement therapy, estrogen creams, or birth control pills, injections, implants, skin patches, and vaginal rings or vaginal suppositories).

Other drugs may interact with anastrozole, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Popular FAQ

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Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Arimidex only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer

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