If you have breast cancer, your doctor may recommend Arimidex as a treatment option for you.

Arimidex is a prescription medication used in females* who’ve gone through menopause. It’s used to treat certain forms of:

  • hormone-receptor positive (HR+) early stage breast cancer, as an adjuvant (post-surgery) treatment
  • HR+ or HR-unknown breast cancer that’s locally advanced or metastatic (has spread to other areas of the body), as the first treatment
  • advanced breast cancer that has worsened after taking tamoxifen (Nolvadex, Soltamox)

Arimidex is not approved for use in children, males,* or females who haven’t gone through menopause.

To learn more about the forms of breast cancer that Arimidex treats, see the “What is Arimidex used for?” section below.

* In this article, we use the terms “female” and “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Arimidex basics

Arimidex contains the active drug anastrozole. This drug is also available as a generic.

Arimidex comes as a tablet that you’ll swallow once per day. It belongs to a group of drugs called aromatase inhibitors.

Read on to learn about Arimidex’s side effects, uses, and more.

Find answers below to some commonly asked questions about Arimidex.

Is Arimidex used for bodybuilding?

Arimidex is not currently approved for bodybuilding purposes. It’s only approved to treat certain forms of breast cancer.

Arimidex is sometimes taken to lower estrogen levels that are high due to anabolic steroid use. High estrogen levels can cause side effects such as gynecomastia (unusual breast gland enlargement). Some people use Arimidex to help reduce such side effects.

Using Arimidex this way is not recommended, and may not be safe. You should not take Arimidex or other drugs unless they’re prescribed for you. In fact, the World Anti-Doping Agency lists aromatase inhibitor drugs as banned substances. Arimidex is a type of aromatase inhibitor.

It’s not known what side effects Arimidex may cause if taken for bodybuilding or whether the drug could lead to more serious problems if used this way. Its dosage for this use also isn’t known, such as the dosage if taken during steroid cycles.

See this article for details about Arimidex and bodybuilding. You might also have questions such as how much Arimidex would be taken with 200 mg of testosterone, or the differences between Arimidex versus Aromasin. Your doctor can help answer such questions and determine whether Arimidex is safe for you.

Do doctors prescribe Arimidex for use in men?

It’s possible. Arimidex is only approved for use in certain females* who’ve gone through menopause. This is because it’s only been studied in females.

But doctors might prescribe Arimidex for off-label use in males* to treat breast cancer that’s fueled by estrogen. Off-label means using a drug for a purpose other than what it’s been approved for.

Arimidex may also be prescribed off-label for certain males who are taking testosterone replacement therapy (TRT). TRT can cause increased estrogen levels in the body, and your doctor might prescribe Arimidex to lower estrogen levels.

Side effects in females may differ from those in males. Recommended dosages may differ as well.

If you’re a male and you’re interested in taking Arimidex, talk with your doctor. They can help determine if Arimidex is a safe option for you.

* In this article, we use the terms “male” and “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

How soon will side effects of Arimidex start? Are there side effects after using the drug for 5 years?

Side effects from Arimidex vary, but can start right after your first dose. Some may occur sooner than others. For example, you can experience headaches, nausea, or vomiting after only one dose of Arimidex.

Other side effects of Arimidex may take longer to happen. For example, side effects such as osteoporosis (weakened bones) or liver problems may not occur for months or years after taking the drug. Your doctor will monitor you for these side effects.

It’s possible to have any of the side effects from Arimidex even after taking the drug for a long time, such as 5 years.

If you have questions about specific side effects or side effects that may occur after taking Arimidex for years, talk with your doctor.

How much does Arimidex increase survival? What’s the percentage of breast cancer recurrence during Arimidex treatment?

Arimidex has been shown to increase breast cancer survival rates. Your type of breast cancer and how advanced it is (how much it has spread) affects how likely it is to recur (worsen or return).

In a study of females taking Arimidex as a first treatment for advanced breast cancer, it took an average of 11.1 months for the cancer to worsen. In comparison, in females who took tamoxifen (Nolvadex, Soltamox), it took an average of 5.6 months before their cancer worsened.

In this study, Arimidex wasn’t compared with a placebo (a treatment with no active drug). So it’s not known how much the drug might improve survival or recurrence compared with no treatment.

If you’d like to learn more about Arimidex’s effectiveness for your type of cancer, talk with your doctor. They can help determine the best treatment option for your condition and what to expect from your treatment.

Is Arimidex a steroid, chemotherapy drug, or estrogen blocker? How much does it lower estrogen levels?

Arimidex is considered an estrogen blocker because it decreases the amount of the hormone estrogen in your body. It isn’t a steroid drug or a type of chemotherapy (traditional drugs used to treat cancer).

Arimidex belongs to a class of drugs called aromatase inhibitors. It works by blocking an enzyme (a type of protein) called aromatase. This enzyme works to change hormones into estrogen.

By blocking this change, Arimidex decreases the amount of estrogen in your body. This decreases the growth of breast cancer.

In studies, Arimidex lowered levels of estradiol (a form of estrogen) by about 70% within 24 hours. After 14 days of treatment, estradiol levels were lowered by about 80%. And estradiol levels continued to be reduced for 6 days after stopping treatment.

Is Arimidex similar to Nolvadex or Clomid?

It’s possible that your doctor may recommend Arimidex, tamoxifen (Nolvadex, Soltamox) or clomiphene (Clomid) for similar uses. But these medications belong to different groups of drugs and work in different ways.

Arimidex and Nolvadex are both used to treat certain forms of breast cancer. They both work by lowering estrogen levels, but in different ways. They have different side effects and dosages, as well.

Clomid is not approved to treat breast cancer. But the drug does lower estrogen levels. It’s used to stimulate (activate) ovulation in females who are trying to become pregnant. It can also be prescribed off-label for other uses. Off-label means using a drug for a purpose other than what it’s been approved for.

Talk with your doctor about the best treatment plan for your condition. They can help you determine if Arimidex, Nolvadex, or Clomid is the best treatment option for you.

What happens when you stop taking Arimidex? Can you stop it ‘cold turkey’?

If you’re thinking about stopping Arimidex, talk with your doctor about the best way to do this. Sometimes, they may recommend stopping Arimidex even after 5 years of treatment or more.

Your doctor may recommend that you stop taking Arimidex “cold turkey,” meaning all at once. Its dosage doesn’t usually need to be decreased slowly over time. If you’re continuing treatment for breast cancer, your doctor may recommend switching to a different drug when you stop Arimidex.

You may want to talk with your doctor about how long side effects last after stopping Arimidex. How long they last may depend on which side effects you experience.

For example, if you have nausea, it may go away right after you stop taking Arimidex. Other side effects such as liver problems or osteoporosis (weakened bones) may remain even after you stop treatment.

You should not stop taking Arimidex without first discussing it with your doctor.

Like most drugs, Arimidex may cause mild or serious side effects. The lists below describe some of the more common side effects it may cause. These lists don’t include all possible side effects.

Keep in mind that side effects of a drug can depend on:

  • your age
  • other health conditions you have
  • other medications you take

Your doctor or pharmacist can tell you more about the potential side effects of Arimidex. They can also suggest ways to help reduce side effects.

Mild side effects

Here’s a list of some of the mild side effects Arimidex can cause. To learn about other mild side effects, talk with your doctor or pharmacist, or read Arimidex’s prescribing information.

Mild side effects of Arimidex that have been reported include:

  • hot flashes
  • weakness
  • pain, such as bone pain, joint pain, or back pain
  • sore throat
  • nausea or vomiting
  • rash
  • high blood pressure
  • insomnia (trouble falling asleep or staying asleep)
  • headache
  • water retention (excess fluid in your body)*
  • cough
  • hair loss*

Mild side effects of many drugs may go away within a few days to a couple of weeks. But if they become bothersome, talk with your doctor or pharmacist.

Serious side effects

Serious side effects from Arimidex can occur, but they aren’t common. If you have serious side effects from Arimidex, call your doctor right away. But if you think you’re having a medical emergency, you should call 911 or your local emergency number.

Serious side effects of Arimidex that have been reported include:

* For more information about this side effect, see the “Side effect focus” section below.

Side effect focus

Learn more about some of the side effects Arimidex may cause.

Water retention

You may experience water retention (excess fluid in your body) from taking Arimidex. This can cause swelling, which tends to occur most often in the ankles, feet, or legs. This was a common side effect reported in people taking Arimidex in studies.

What might help

If you have swelling or water retention from taking Arimidex, talk with your doctor about how to treat this. They may recommend that you take a medication along with Arimidex to reduce swelling.

Hair loss

It’s possible to have hair loss or hair thinning with Arimidex. This side effect was only reported in people taking the drug for advanced breast cancer. Hair loss was not a common side effect in studies.

What might help

If you notice hair loss or hair thinning during your treatment with Arimidex, talk with your doctor. They may recommend ways to reduce this side effect or keep it from getting worse.

Blood clots

Very rarely, it’s possible to develop blood clots from taking Arimidex. In studies, blood clots were reported in the lungs, eyes, and legs.

Symptoms of a blood clot may include:

  • swelling, redness, or warmth in one leg
  • chest pain
  • trouble breathing
  • pain in your eyes or loss of vision

What might help

If you develop symptoms of a blood clot, it’s important to see a doctor right away. Blood clots can be life threatening, and should be treated as soon as possible.

Also talk with your doctor about your risk of blood clots. If you’re taking certain medications or have other medical conditions, your risk may be higher.

Throughout your treatment with Arimidex, your doctor will monitor you for symptoms of blood clots. If you develop a clot, your doctor will treat it and may recommend a different treatment for your breast cancer.

Allergic reaction

Although uncommon, some people may have an allergic reaction to Arimidex.

Symptoms of a mild allergic reaction can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include swelling under your skin, typically in your eyelids, lips, hands, or feet. They can also include swelling of your tongue, mouth, or throat, which can cause trouble breathing or swallowing.

Call your doctor right away if you have an allergic reaction to Arimidex. But if you think you’re having a medical emergency, call 911 or your local emergency number.

You may wonder how Arimidex compares with Aromasin and other alternatives. Read on to learn more about how this drug is similar and different from others.

Arimidex vs. Aromasin

To see how Arimidex compares with Aromasin, check out this detailed breakdown. Talk with your doctor if you’d like to know more about these drugs.

Arimidex vs. tamoxifen

If you’d like, ask your doctor whether Arimidex or tamoxifen is better for your condition. And see this comparison for more information about the drugs.

Arimidex vs. letrozole

Read this article to find out how Arimidex and letrozole are alike and different. Check with your doctor about which drug is right for you.

Your doctor will recommend the dosage of Arimidex that’s right for you. Below are commonly used dosages, but always take the dosage your doctor prescribes.

Form and strength

Arimidex comes as a tablet that you take by mouth. It’s available in a strength of 1 milligram (mg).

Recommended dosage

The recommended dosage of Arimidex is one tablet, once daily.

Questions about Arimidex’s dosage

  • What if I miss a dose of Arimidex? If you miss your dose of Arimidex, take it as soon as you remember, unless it’s almost time for your next dose. In that case, skip the dose you missed and continue with your normal schedule. Never take two doses of Arimidex to make up for a missed dose. If you miss a dose and you’re not sure when to take your next dose, talk with your doctor or pharmacist.
  • Will I need to use Arimidex long term? If Arimidex works for you, your doctor will likely recommend that you take it long term.
  • How long does Arimidex take to work? Arimidex begins working to treat your breast cancer after you take your first dose. You may not notice any changes from taking Arimidex. But your doctor will monitor your condition during your treatment to see how well the drug is working.

Costs of prescription drugs can vary depending on many factors. These factors include what your insurance plan covers and which pharmacy you use. To find current prices for Arimidex tablets in your area, visit GoodRx.com.

Arimidex is available as the generic drug anastrozole. Generics usually cost less than brand-name drugs. Talk with your doctor if you’d like to know about taking generic anastrozole.

If you have questions about how to pay for your prescription, talk with your doctor or pharmacist. You can also visit the Arimidex manufacturer’s website to see if they have support options.

You can also check out this article to learn more about saving money on prescriptions.

Arimidex is used to treat certain forms of breast cancer in females* who’ve gone through menopause.

Breast cancer causes cells in your breast to grow quickly and out of control. This fast growth can cause a tumor to form in your breast. The cancer cells may also spread to other parts of the body.

Your doctor may test your breast cancer to determine if it’s hormone-receptor positive (HR+). This means the cancer is affected by hormones such as estrogen. Arimidex works by lowering estrogen levels in your body, which can decrease cancer growth.

Specifically, Arimidex is used to treat:

  • Early stage HR+ cancer. Early stage cancer is cancer that has not yet spread to lymph nodes or other parts of your body. For this use, Arimidex is used as an adjuvant treatment. This is treatment to prevent cancer from coming back or worsening after it’s been surgically removed.
  • Locally advanced or metastatic breast cancer that’s HR+ or HR-unknown. Locally advanced means the cancer has spread to your armpit lymph nodes or areas that are close to your breast. Metastatic means the cancer has spread to other areas of your body. And HR-unknown means that the cancer might or might not be affected by hormones.
  • Advanced breast cancer that has worsened after taking tamoxifen. Tamoxifen (Nolvadex, Soltamox) is another drug used for breast cancer treatment. For this use, Arimidex can be taken for cancer that’s HR+, HR negative (HR-), or HR-unknown. It’s important to note that Arimidex is rarely effective for cancer that:
    • hasn’t improved with past tamoxifen treatment, or
    • is estrogen-receptor negative

Arimidex is not approved for use in children, males,* or females who haven’t gone through menopause.

* In this article, we use the terms “female” and “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Before you start taking Arimidex, talk with your doctor about any other medical conditions you have and other medications you take. In some cases, Arimidex may not be the best treatment option for you. Below are some medications and medical conditions that you should discuss with your doctor before starting Arimidex.

Interactions

Taking a medication with certain vaccines, foods, and other things can affect how the medication works. These effects are called interactions.

Before taking Arimidex, be sure to tell your doctor about all medications you take, including prescription and over-the-counter types. Also describe any vitamins, herbs, or supplements you use. Your doctor or pharmacist can tell you about any interactions these items may cause with Arimidex.

Interactions with drugs or supplements

Arimidex can interact with several types of drugs. These drugs include:

  • Drugs that contain the hormone estrogen. Arimidex works by lowering estrogen levels in your body. Taking drugs that increase your estrogen levels may decrease the effectiveness of Arimidex. Due to this risk, your doctor will likely recommend that you avoid taking drugs that contain estrogen while you’re taking Arimidex. Examples include hormone replacement therapy and estrogen creams.
  • Tamoxifen. In studies, taking Arimidex with tamoxifen was not a more effective treatment option than taking tamoxifen alone. And taking both drugs increased the risk of side effects from treatment. Your doctor will likely not recommend taking these medications together.

This list does not contain all types of drugs that may interact with Arimidex. Your doctor or pharmacist can tell you more about these interactions and any others that may occur with use of Arimidex.

Warnings

Arimidex may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take Arimidex. Factors to consider include those in the list below.

  • High cholesterol levels. Arimidex may increase your cholesterol levels. If you have high cholesterol, this medication may make it worse. Your doctor may recommend medication to lower your cholesterol levels while you’re taking Arimidex.
  • Allergic reaction. If you’ve had an allergic reaction to Arimidex or any of its ingredients, your doctor will likely recommend that you don’t take Arimidex. Ask your doctor what other medications are better options for you.
  • Osteoporosis (weakened bones). If you have osteoporosis, tell your doctor before starting Arimidex. This medication may increase your risk of osteoporosis or broken bones, and can make existing osteoporosis worse. Your doctor may monitor your bone strength while you’re taking Arimidex, or may recommend a different treatment option for you.
  • Ischemic heart disease (a heart condition that affects blood flow to your heart). Tell your doctor about any heart problems you have, especially ischemic heart disease (also called coronary artery disease). Arimidex may increase the risk of serious heart or blood vessel problems in females* with ischemic heart disease. These problems can include a heart attack or stroke. Your doctor may recommend more frequent monitoring of your heart health during Arimidex treatment, or a different treatment option.
  • Liver problems. Arimidex may cause increased liver enzyme levels, which may be a sign of liver damage. If you already have liver problems, Arimidex can make your liver problems even worse. Your doctor may monitor your liver function more often than usual if you take Arimidex. Or they may recommend a different medication for your condition.
  • Females who have not gone through menopause. Arimidex is only approved for use in females who’ve gone through menopause. It’s not known if the drug is effective when used in females who haven’t gone through menopause. Your doctor will likely recommend a different medication for you.

* In this article, we use the terms “female” and “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Arimidex and alcohol

There are no known interactions between Arimidex and alcohol. But they may cause similar side effects, such as nausea, vomiting, or headache. So alcohol may worsen certain side effects of Arimidex.

Also, Arimidex and alcohol can each cause liver damage. So the two together may increase your risk of developing a liver condition, such as liver failure.

Talk with your doctor about how much alcohol, if any, is safe for you to drink during your Arimidex treatment.

Pregnancy and breastfeeding

Arimidex may cause harm to a fetus if taken during pregnancy or within 3 weeks of becoming pregnant. Due to this risk, your doctor will likely recommend that you do not take Arimidex if you’re pregnant or planning to become pregnant. They’ll also likely recommend that you do not breastfeed while taking Arimidex and for at least 2 weeks after your last dose.

If you’re able to become pregnant, your doctor will likely recommend that you take a pregnancy test before starting Arimidex. You’ll also be advised to use an effective form of birth control throughout treatment and for at least 3 weeks after your last dose.

Your doctor will explain how you should take Arimidex. They’ll also explain how much to take and how often. Be sure to follow your doctor’s instructions.

Taking Arimidex

Arimidex comes as a tablet you’ll take by mouth.

Questions about taking Arimidex

  • Can Arimidex be chewed, crushed, or split? No, Arimidex tablets should not be chewed, crushed, or split. You should swallow your Arimidex tablet whole. If you have trouble with this, see this article for tips on how to swallow pills.
  • Should I take Arimidex with food? You can take Arimidex with or without food.
Questions for your doctor

You may have questions about Arimidex and your treatment plan. It’s important to discuss all your concerns with your doctor.

Here are a few tips that might help guide your discussion:

  • Before your appointment, write down questions such as:
    • How will Arimidex affect my body, mood, or lifestyle?
  • Bring someone with you to your appointment if doing so will help you feel more comfortable.
  • If you don’t understand something related to your condition or treatment, ask your doctor to explain it to you.

Remember, your doctor and other healthcare professionals are available to help you. And they want you to get the best care possible. So, don’t be afraid to ask questions or offer feedback on your treatment.

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

What to do in case you take too much Arimidex

Call your doctor if you think you’ve taken too much Arimidex. You can also call 800-222-1222 to reach the American Association of Poison Control Centers or use its online resource. However, if you have severe symptoms, immediately call 911 or your local emergency number. Or, go to the nearest emergency room.

Before you start taking Arimidex, talk to your doctor about any questions you may have. Here are some questions you may wish to discuss with your doctor:

  • Will Arimidex cause memory loss?
  • What other treatment options are available if I can’t take Arimidex?
  • Is there an Arimidex dosage for gynecomastia?
  • How can I prevent Arimidex side effects from occurring?

If you would like to learn more about breast cancer treatment options, see this article. You may also wish to learn about complementary and alternative medicine for breast cancer.

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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.