Arimidex (anastrozole) is a prescription drug that’s taken to treat certain types of breast cancer in adults. The drug comes as a tablet that you swallow. It’s usually taken once per day.

Arimidex is prescribed to treat the following conditions:

Specifically, Arimidex is only approved to treat these types of breast cancer in females* who have already experienced menopause.

The active ingredient in Arimidex is anastrozole.

Arimidex belongs to a group of drugs called aromatase inhibitors.

This article describes the dosage of Arimidex, as well as its strength and how to take it. To learn more about Arimidex, see this in-depth article.

* Sex and gender exist on spectrums. Use of the term “male” and “female” in this article refers to sex assigned at birth.

Breast cancer term definitions
  • “Early” means that the cancer hasn’t spread beyond your breast or the lymph nodes in your armpit.
  • “Advanced” means that the cancer has spread into areas of your body near your breast or the lymph nodes in your armpit.
  • “Metastatic” means that the cancer has spread outside of areas near your breast or the lymph nodes in your armpit.

Below, you’ll find information about the dosage of Arimidex that’s typically prescribed.

What is Arimidex’s form?

Arimidex comes as a tablet that you swallow.

What strength does Arimidex come in?

Arimidex is available in one strength: 1 milligram (mg).

What is the typical dosage of Arimidex?

The information below describes the dosage that’s commonly used or recommended. But be sure to take the dosage your doctor prescribes for you. They’ll determine the best dosage to fit your needs.

Dosage for early breast cancer, advanced breast cancer, and metastatic breast cancer

Arimidex may be prescribed to treat certain forms of early, advanced, and metastatic breast cancer.

The usual dosage of Arimidex is the same for each condition it’s prescribed to treat. This dosage is one tablet (1 mg) taken once per day.

Is Arimidex used long term?

In some cases, yes, Arimidex may be taken as a long-term treatment. How long you’ll take Arimidex for depends on what condition you’re taking it to treat. If you and your doctor determine that Arimidex is safe and effective for you, you might take it long term.

Use for early breast cancer

Doctors may prescribe Arimidex after you’ve already had surgery to remove your breast cancer. When prescribed for this purpose, Arimidex is usually taken for as long as it continues to be safe and effective for you. If your cancer spreads or comes back, your doctor will likely stop prescribing Arimidex.

Use for advanced or metastatic breast cancer

When taken to treat advanced or metastatic breast cancer, you’ll take Arimidex for as long as your doctor recommends. In studies, when taken for this purpose, Arimidex was typically taken for 5 years.

Here are answers to some common questions about Arimidex dosage.

Is there an FDA-approved Arimidex dosage used for bodybuilding?

No, there isn’t an Arimidex dosage for bodybuilding that’s approved by the Food and Drug Administration (FDA).

Arimidex is prescribed to treat certain types of breast cancer in adult females who’ve gone through menopause. The drug works by lowering estrogen levels in the body.

However, some bodybuilders take Arimidex to lessen side effects from anabolic steroids. Anabolic steroids are a human-made form of a hormone called testosterone. Bodybuilders may use these drugs in cycles (starting, stopping, and restarting their use). They’re used as a form of testosterone replacement therapy to help muscles grow.

This type of steroid use can cause an increase in estrogen levels. In males, higher estrogen levels can cause gynecomastia (breast growth in males). When taken with testosterone, Arimidex offsets the increase in estrogen levels. This helps prevent breast growth in males.

However, the FDA hasn’t approved Arimidex for bodybuilding purposes, and it’s illegal to buy Arimidex for this purpose. You should not take Arimidex without a prescription from a healthcare professional. And you should not take the drug for conditions it hasn’t been prescribed to treat.

If you have questions about approved uses for Arimidex, talk with your doctor.

Will my dosage of Arimidex change if I take it with other drugs to treat my breast cancer?

It’s not likely. Depending on the type of breast cancer you have, your doctor may prescribe Arimidex with another cancer treatment. But your Arimidex dosage will probably stay the same.

For advanced or metastatic breast cancer, Arimidex is typically taken in combination with targeted therapies. Targeted therapies work to attack cancer cells while causing little harm to healthy cells. Examples of targeted therapies include trastuzumab (Herceptin) and pertuzumab (Perjeta).

You may also take other medications to help manage the side effects of Arimidex. For example, osteoporosis (weakened bones) is a common side effect of the drug. So, your doctor may prescribe drugs such as risedronate (Actonel) or alendronate (Fosamax) to help protect your bones.

If you have questions about taking Arimidex with other breast cancer treatments, talk with your doctor.

If you forget to take your daily dose of Arimidex, take your missed dose as soon as you remember. But if it’s almost time to take your next dose, skip your missed dose. Then, take your next dose at your usual time. You should not take any extra doses of Arimidex to make up for a missed dose.

If you’re not sure if you should take or skip your dose, ask your doctor or pharmacist.

If you need help remembering to take your dose of Arimidex on time, try using a medication reminder. This can include setting an alarm, downloading a reminder app, or setting a timer on your phone. A kitchen timer can also work.

The dosage of Arimidex you’re prescribed may depend on certain factors. The main factors that could affect your dosage are the type and severity of the breast cancer you’re taking Arimidex to treat.

Your doctor will consider these factors when determining the most appropriate dosage for you.

Be sure to take Arimidex exactly as your doctor prescribes.

Arimidex comes as a tablet you’ll swallow. Your doctor will likely have you take your Arimidex dose once per day.

The drug can be taken at any time of day. But, if possible, it’s best to take your dose at the same time each day. This helps keep a consistent amount of the medication in your body at all times.

You can take Arimidex with or without food.

Do not take more Arimidex than your doctor prescribes. Doing so can lead to serious side effects.

What to do in case you take too much Arimidex

Call your doctor right away if you think you’ve taken too much Arimidex. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resource. But if you have severe symptoms, call 911 (or your local emergency number) immediately or go to the nearest emergency room.

The sections above describe the typical dosage provided by the drug manufacturer. If your doctor recommends Arimidex for you, they’ll prescribe the dosage that’s right for you.

Remember, you shouldn’t change your dosage of Arimidex without your doctor’s approval. Only take Arimidex exactly as prescribed.

If you have questions or concerns about your current dosage, talk with your doctor. Here are examples of questions you may want to ask your doctor:

  • Should my dosage change if I eat certain foods while taking Arimidex?
  • Does my dosage of Arimidex need to change if I’m taking certain other drugs along with it?
  • How long will Arimidex keep working for me after I’ve stopped taking the drug?

Q:

Instead of taking one Arimidex tablet once per day, can I take one-half of a tablet twice daily?

Anonymous

A:

It isn’t recommended. You should not split, crush, or chew Arimidex tablets. Doing so may make Arimidex less effective in treating your breast cancer.

It’s important to take your dosage of Arimidex exactly as prescribed by your doctor. If you have trouble taking Arimidex once daily, talk with your doctor.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.