Arimidex (anastrozole) is a prescription medication used to treat specific types of breast cancer in adults. It’s supplied as an oral tablet that you swallow, typically once a day.
Arimidex may be prescribed for:
- early breast cancer that is hormone receptor–positive (HR-positive)
- advanced or metastatic breast cancer that is HR-positive, HR-negative, or HR-unknown
Arimidex is approved specifically to treat these breast cancer types in people assigned female at birth who have already undergone menopause.
The drug’s active component is anastrozole.
Arimidex is part of a class of medicines known as aromatase inhibitors.
This article explains Arimidex dosing, available strength, and how it’s taken. For more detailed information, see this comprehensive article.
*Sex and gender exist on spectra. The terms “male” and “female” used here refer to sex assigned at birth.
Breast cancer term definitions “Early” indicates the cancer hasn’t extended beyond the breast or the nearby armpit lymph nodes. “Advanced” means the cancer has spread into regions close to the breast or armpit lymph nodes. “Metastatic” denotes cancer that has spread beyond those nearby areas.
What is Arimidex’s dosage?
Below is information about commonly prescribed Arimidex dosing.
What form does Arimidex come in?
Arimidex is available as a tablet to swallow.
What strength is Arimidex available in?
Arimidex is sold in a single strength: 1 milligram (mg).
What is the usual Arimidex dosage?
The following outlines the commonly recommended dosage. Always follow the dose your doctor prescribes. They will decide the best dose for you.
Dosage for early, advanced, and metastatic breast cancer
Arimidex may be used to treat certain types of early, advanced, and metastatic breast cancer.
The standard dose for these indications is the same: one tablet (1 mg) taken once daily.
Is Arimidex a long-term treatment?
In some situations, yes—Arimidex can be used long term. The duration depends on the condition being treated. If you and your clinician find Arimidex to be safe and effective, you may continue it long term.
Use for early breast cancer
Physicians may advise Arimidex after surgery to remove breast cancer. When prescribed for this reason, it’s generally continued as long as it remains safe and effective. If the cancer recurs or spreads, your doctor may discontinue Arimidex.
Use for advanced or metastatic breast cancer
For advanced or metastatic breast cancer, Arimidex is taken for the period recommended by your physician. In clinical trials, use for this purpose was often around 5 years.
Frequently asked questions
Below are answers to common questions about Arimidex dosing.
Is there an FDA-approved Arimidex dose for bodybuilding?
No. The U.S. Food and Drug Administration (FDA) has not approved any Arimidex dose for bodybuilding.
Arimidex is prescribed to treat specific types of breast cancer in postmenopausal adults assigned female at birth. It works by reducing estrogen levels in the body.
Some bodybuilders use Arimidex to try to minimize side effects from anabolic steroid use. Anabolic steroids are synthetic forms of the hormone testosterone and are sometimes used in cycles to promote muscle growth.
Such steroid use can elevate estrogen levels. In people assigned male at birth, increased estrogen can lead to gynecomastia (breast enlargement). When combined with testosterone, Arimidex may counteract the estrogen rise, helping reduce the risk of breast enlargement.
However, the FDA has not authorized Arimidex for bodybuilding, and obtaining it for that purpose is illegal. You should not take Arimidex without a prescription and should avoid using it for unapproved conditions.
If you have questions about approved uses of Arimidex, discuss them with your healthcare provider.
Will my Arimidex dose change when taken with other cancer drugs?
Probably not. Depending on your cancer type, your doctor might prescribe Arimidex alongside another cancer therapy, but the Arimidex dose usually remains unchanged.
For advanced or metastatic disease, Arimidex is often paired with targeted therapies, which aim to attack cancer cells while sparing healthy tissue. Examples of targeted drugs include trastuzumab (Herceptin) and pertuzumab (Perjeta).
You may also receive medications to manage Arimidex side effects. For instance, osteoporosis (weakened bones) is a known side effect, so your doctor might prescribe agents like risedronate (Actonel) or alendronate (Fosamax) to help protect bone health.
If you’re unsure about combining Arimidex with other breast cancer treatments, ask your doctor.
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What if I miss a dose?
If you miss a daily Arimidex dose, take it as soon as you remember. If it’s nearly time for your next dose, skip the missed dose and take the next one at the usual time. Do not take extra doses to make up for a missed one.
If you’re uncertain whether to take a missed dose, contact your doctor or pharmacist.
To help remember your daily dose, use medication reminders such as alarms, a reminder app, phone timers, or a kitchen timer.
What factors influence my dose?
Your prescribed Arimidex dose may depend on factors such as the type and severity of the breast cancer being treated.
Your clinician will weigh these factors when selecting the appropriate dose for you.
How should Arimidex be taken?
Take Arimidex exactly as directed by your doctor.
Arimidex is an oral tablet usually taken once a day.
You can take the medication at any time of day, but it’s best to take it at the same time each day to maintain steady drug levels in your body.
Arimidex may be taken with or without food.
What should I do in case of an overdose?
Do not take more Arimidex than prescribed; doing so can cause serious adverse effects.
If you think you’ve taken too much Arimidex
Contact your doctor immediately if you suspect an overdose. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resource. If you have severe symptoms, call 911 (or your local emergency number) or go to the nearest emergency department right away.
What should I ask my doctor?
The above sections describe typical dosing from the manufacturer. If your clinician prescribes Arimidex, they will tailor the dose to your needs.
Never change your Arimidex dose without approval from your doctor. Take Arimidex only as prescribed.
If you have concerns about your dose, discuss them with your doctor. Questions you might ask include:
- Should I change my dose if I eat certain foods while taking Arimidex?
- Does my Arimidex dose need adjustment if I take other medications?
- How long will Arimidex continue to be effective after I stop taking it?
Ask a pharmacist
Q:
Can I split one Arimidex tablet into halves and take one half twice daily instead of one whole tablet once daily?
A:
No. Splitting, crushing, or chewing Arimidex tablets is not recommended. Altering the tablet may reduce its effectiveness against your breast cancer.
Take Arimidex exactly as prescribed. If taking one tablet once daily is difficult, discuss alternatives with your healthcare provider.
Disclaimer: Efforts have been made to ensure the accuracy, completeness, and currency of the information provided. This article is not a replacement for professional medical advice. Always consult your doctor or another qualified healthcare professional before starting any medication. Drug information can change and may not encompass all uses, directions, precautions, warnings, interactions, allergic reactions, or adverse effects. The lack of warnings or other information for a given drug does not mean the drug or combination is safe, effective, or suitable for all patients or all uses.
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