Arimidex is a brand-name oral tablet that’s prescribed for certain types of breast cancer. Arimidex contains the active ingredient anastrozole and is a type of hormone therapy.
Some types of breast cancer need hormones such as estrogen to grow. Hormone therapies for breast cancer, such as Arimidex, work by lowering the estrogen in your body, so the cancer cannot grow.
The Food and Drug Administration (FDA) has approved Arimidex to treat the following types of breast cancer in females who have gone through menopause:
- Early hormone receptor-positive (HR-positive) breast cancer. For early breast cancer that is HR-positive, Arimidex is given to lower the risk of the breast cancer coming back or spreading after it’s already been treated with surgery. This type of treatment is called adjuvant treatment.
- Locally advanced or metastatic breast cancer that’s either HR-positive or HR-unknown. Locally advanced or metastatic breast cancer typically can’t be treated with surgery. For these conditions, Arimidex is given as a first-line treatment. With first-line treatment, the drug is the first treatment used for the cancer.
- Locally advanced or metastatic breast cancer that’s come back or spread after treatment with the cancer drug tamoxifen. Note that if your breast cancer is estrogen receptor-negative (ER-negative), or it didn’t improve with tamoxifen treatment in the past, it’s unlikely to improve with Arimidex.
For details about these uses of Arimidex, see the “Arimidex (anastrozole) uses” section below.
Note: Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.
Drug details
You’ll find key information about Arimidex below.
- Drug class: aromatase inhibitor
- Drug form: oral tablet
- Generic available? yes
- Prescription required? yes
- Controlled substance? no
- Year of FDA approval: 1995
Arimidex contains the active ingredient anastrozole, and it’s available in a generic version. A generic drug is an exact copy of the active ingredient in a brand-name medication. The generic is considered to be just as safe and effective as the original drug. Generics also tend to cost less than brand-name drugs.
Arimidex can cause mild or serious side effects. Listed below are some of the key side effects that may occur while taking Arimidex. These lists do not include all possible side effects. And your side effects may vary from those listed below depending on the condition you’re using Arimidex to treat.
For more information on the possible side effects of Arimidex, see this article. You can also talk with your doctor or pharmacist. They can give you tips on how to deal with any side effects that may be bothersome.
Note: The Food and Drug Administration (FDA) tracks side effects of drugs it has approved. If you would like to report to the FDA a side effect you’ve had with Arimidex, you can do so through MedWatch.
When side effects of Arimidex may start
It’s possible to have certain side effects of Arimidex soon after you start taking the medication. This is because Arimidex lowers your body’s estrogen level significantly within 24 hours after taking your first dose. Lowering your estrogen level may lead to side effects that are similar to those of menopause, such as hot flashes and insomnia.
Other side effects can take much longer to develop, such as thinning and weakening of your bones and increased cholesterol levels. You’re unlikely to notice side effects such as these, but your doctor will monitor you for them.
How long side effects of Arimidex may last
It’s hard to say how long your side effects will last, as each person’s reaction to the drug can be different. How long you’ll have side effects from the drug depends on how your body reacts to Arimidex.
If you’re concerned about side effects that don’t seem to be improving, talk with your doctor. They can recommend ways to help you manage the side effects.
Do side effects of Arimidex get worse over time?
Some Arimidex side effects can get worse over time. However, some mild side effects may go away or improve over time. These include nausea, headache, and dizziness.
For some people, side effects may occur off and on throughout treatment, such as hot flashes, joint pain, or insomnia. Your doctor can also discuss symptoms of Arimidex side effects to watch for. If you experience any such symptoms, especially if they are severe or bothersome, be sure to contact your doctor right away.
Your doctor will monitor you for certain side effects that could become serious if allowed to worsen, such as thinning bones or high cholesterol levels. Your doctor will likely order tests before and during treatment to monitor for these changes.
Mild side effects
The mild side effects* of Arimidex can include:
- hot flashes
- feeling weak
- bone pain
- arthritis
- nausea and vomiting
- rash
- insomnia
- headache
- peripheral edema (swelling in your legs, ankles, or feet that’s caused by fluid retention)
- lymphedema (buildup of lymphatic fluid in the tissues of your arm, which causes swelling in the area)
- sore throat
- dizziness
- mood changes, such as depression
- carpal tunnel syndrome (a nerve condition that affects your wrist), which may cause pain, tingling, or numbness in your hand
- fatigue†
- back or joint pain†
- weight gain†
* This is a partial list of mild side effects of Arimidex. To learn about other mild side effects, talk with your doctor or pharmacist, or view the drug’s prescribing information.
† For more information about this side effect, see the “Side effect details” section below.
Most of these side effects may go away within a few days or a couple of weeks. But if they become more severe or don’t go away, talk with your doctor or pharmacist.
Serious side effects
Serious side effects from Arimidex aren’t common, but they can occur. Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life threatening or if you think you’re having a medical emergency.
Serious side effects and their symptoms can include:
- Liver problems, such as hepatitis (inflammation in your liver). Symptoms can include:
- generally not feeling well
- pain on the right side of your abdomen
- jaundice (yellowing of your skin or the whites of your eyes)
- Skin reactions. Symptoms can include:
- skin sores or ulcers
- blisters
- Reduced bone mineral density (weakened bones). Symptoms can include:
- bone fractures
- decreased height
- Increased cholesterol level.
- Heart problems. Symptoms can include:
- new or worsening chest pain
- shortness of breath
- allergic reaction*
* For more information about this side effect, see the “Side effect details” section below.
Side effect details
You may wonder how often certain side effects occur with this drug. Here’s some detail on several of the side effects this drug may cause.
Allergic reaction
As with most drugs, some people can have an allergic reaction after taking Arimidex. But it’s not known how often this occurs in people using Arimidex.
Symptoms of a mild allergic reaction can include:
- skin rash
- itchiness
- hives (raised spots on the skin)
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
- swelling of your tongue, mouth, or throat
- trouble breathing
Call your doctor right away if you have a severe allergic reaction to Arimidex. Call 911 if your symptoms feel life threatening or if you think you’re having a medical emergency.
Side effects after 5 years of treatment
Both the mild and serious side effects of Arimidex that are listed above were seen in females who took the drug for up to 5 years.
Clinical trials of Arimidex followed females with early breast cancer who took the drug for 5 years. (With early breast cancer, the cancer hasn’t spread from either your breast or the lymph nodes in your armpit.) The trials were continued for an additional 5 years after they stopped taking the drug. No new side effects were reported during this additional time.
If you have concerns about the side effects that you may have after Arimidex treatment, talk with your doctor. They can discuss with you what you may expect after treatment.
Note: Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.
Weight gain
Some people using Arimidex may gain weight during treatment. This was a reported side effect in clinical trials of the drug.
Cancer itself as well as cancer treatments can often cause changes in your appetite and body weight. If you’re concerned about weight gain during breast cancer treatment, talk with your doctor. They can recommend ways to help you manage a weight that’s healthy for you.
Back or joint pain
Joint pain, achiness, and stiffness are common side effects of aromatase inhibitors, such as Arimidex. (Aromatase inhibitors are a class of medications.)
In clinical trials, joint pain, aches, and stiffness are common side effects of aromatase inhibitors, such as Arimidex. (Aromatase inhibitors are a class of medication.)
On average, joint pain seems to begin about 6 weeks after starting an aromatase inhibitor. And it may improve after the first year of taking the drug. Various
If you have pain in your joints or your back while you’re taking Arimidex, talk with your doctor. They can recommend ways to help manage your discomfort.
Fatigue
Taking Arimidex can make you feel either weak or fatigued. In clinical trials, weakness and fatigue were fairly common side effects in females taking Arimidex.
Because of this, it’s important to rest while you’re undergoing cancer treatment. However, the
If you feel weakness or fatigue during Arimidex treatment, talk with your doctor about the best ways to manage these side effects.
The following information describes Arimidex dosages that are commonly used or recommended. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to fit your needs.
For additional details on Arimidex’s dosage, see this article.
Drug forms and strengths
Arimidex comes as a tablet that you take by mouth. The drug is available in one strength: 1 milligram (mg).
Dosage for breast cancer
The usual dosage of Arimidex for breast cancer is one 1-mg tablet taken once per day. It’s best to take your dose at the same time each day.
What if I miss a dose?
If you forget to take a dose of Arimidex, take the missed dose as soon as you remember. However, if it’s almost time for your next dose, just skip the missed dose and take your next dose as usual. Don’t take two doses together to make up for a missed dose.
To help make sure that you don’t miss a dose, try setting a reminder on your phone. A medication timer may be useful, too.
Will I need to use this drug long term?
Arimidex is meant to be used as a long-term treatment for breast cancer. If you and your doctor determine that Arimidex is safe and effective for you, you’ll likely take it long term.
The length of time that you’ll take this drug depends on the type of cancer you’re using it to treat. Below we describe the typical length of time that Arimidex is taken. But to know for sure how long you should take Arimidex, talk with your doctor.
For advanced breast cancer
If you’re taking Arimidex to treat advanced breast cancer, you’ll usually take the drug for as long as your doctor feels this treatment is right for you. (With advanced breast cancer, the cancer has either spread to nearby areas or lymph nodes, called locally advanced breast cancer, or spread to other parts of your body, called metastatic breast cancer.)
For early breast cancer
If you’re taking Arimidex as adjuvant treatment of early breast cancer, you’ll usually take the drug for at least 5 years. Adjuvant treatment is used to lower the risk of your breast cancer coming back or spreading after it’s already been treated with surgery. (With early breast cancer, the cancer hasn’t spread from either your breast or the lymph nodes in your armpit.)
It’s not currently known whether Arimidex should be continued after these 5 years. And if so, it’s not known for how long after the first 5 years it should be taken.
Some
In addition, one study found that taking Arimidex for a total of 10 years didn’t provide any more benefit than taking it for a total of 7 years.
How long you take Arimidex for early breast cancer will depend on how likely your breast cancer is to come back. It will also depend on your risk of side effects from treatment.
The Food and Drug Administration (FDA) approves prescription drugs such as Arimidex to treat certain conditions. Arimidex may also be used off-label for other conditions. Off-label use is when a drug that the FDA has approved to treat one condition is prescribed to treat a condition that is not FDA approved.
Arimidex for breast cancer
Arimidex is FDA approved to treat breast cancer in females who’ve gone through menopause.
Specifically, Arimidex is used to treat the following types of breast cancer:
Early hormone receptor-positive (HR-positive) breast cancer. For this type of cancer, Arimidex is given to lower the risk of the breast cancer coming back or spreading after it’s already been treated with surgery. This type of treatment is called adjuvant treatment.
Early breast cancer hasn’t spread from either your breast or the lymph nodes in your armpit. HR-positive cancer is stimulated to grow by hormones, including estrogen.
Locally advanced or metastatic breast cancer that’s either HR-positive or HR-unknown. Locally advanced or metastatic breast cancer typically can’t be treated with surgery. For these conditions, Arimidex is given as a first-line treatment. With first-line treatment, the drug is the first treatment used for the cancer.
Locally advanced breast cancer has spread to nearby areas or lymph nodes, while metastatic breast cancer has spread to other parts of your body. And while HR-positive breast cancer is stimulated to grow by hormones, HR-unknown cancer may or may not be stimulated to grow by hormones.
Locally advanced or metastatic breast cancer that’s come back or spread after treatment with the cancer drug tamoxifen. Note that if your breast cancer is estrogen receptor-negative (ER-negative), or it didn’t improve with tamoxifen treatment in the past, it’s unlikely to improve with Arimidex. (ER-negative cancer doesn’t need estrogen in order to grow.)
Arimidex contains the drug anastrozole. It’s a hormone therapy used for breast cancer. Hormone therapies for breast cancer work by stopping estrogen from stimulating the cancer to grow. Specifically, Arimidex is a type of hormone therapy called an aromatase inhibitor. It works by lowering the amount of estrogen that your body makes.
For more information on these conditions, see our breast cancer hub.
Note: Sex and gender exist on spectrums. Use of the terms “female” and “male” in this article refers to sex assigned at birth.
Effectiveness for breast cancer
One large clinical trial showed that Arimidex was more effective than tamoxifen in treating early HR-positive breast cancer. (Tamoxifen is another hormone therapy used to treat cancer. It’s a standard treatment option for breast cancer, as recommended in current guidelines.)
For advanced breast cancer, clinical trials have shown that Arimidex treatment was either more effective or similarly effective to tamoxifen treatment.
Two studies looked at females with advanced breast cancer that had come back or spread after treatment with tamoxifen. For these females, second-line treatment with Arimidex was similarly effective as treatment with another hormone therapy drug called megestrol.
Other uses for Arimidex
In addition to the uses listed above, Arimidex may be used off-label. Off-label use is when a drug that the FDA has approved to treat one condition is prescribed to treat a condition that is not FDA approved. Below is information on other possible uses for Arimidex.
Arimidex for breast cancer treatment in premenopausal females (off-label use)
Arimidex isn’t FDA approved to treat breast cancer in premenopausal females. (These are females who haven’t gone through menopause.) But sometimes the drug is used off-label in such females to treat hormone receptor-positive (HR-positive) cancers. With HR-positive breast cancer, the cancer is stimulated to grow by hormones.
It’s important to note that Arimidex works by stopping the aromatase enzyme (a type of protein) from working in your body. This enzyme helps to make your body’s estrogen. However, before females reach menopause, most of their estrogen is made by their ovaries. And only a small amount is made by the aromatase enzyme.
While Arimidex stops the aromatase enzyme from working, it doesn’t stop your ovaries from making estrogen.
If you take Arimidex to treat breast cancer before you’ve reached menopause, you’ll also need to take treatment that stops your ovaries from making estrogen. This is typically done with a type of drug called a luteinizing hormone-releasing hormone (LHRH) analog. Treatment may also be done using radiation on your ovaries or by having surgery to remove your ovaries.
If you’d like to know more about using Arimidex for breast cancer before you’ve reached menopause, talk with your doctor.
Arimidex for ovarian cancer (off-label use)
Arimidex isn’t FDA approved to treat ovarian cancer. However, the
Stromal tumors start in tissue inside your ovaries that produces estrogen and progesterone. The hormone therapies that are sometimes used to treat this kind of cancer include aromatase inhibitors, such as Arimidex.
If you have questions about treatment options for ovarian cancer, talk with your doctor.
Arimidex for uterine cancer, including endometrial cancer (off-label use)
Arimidex isn’t FDA approved to treat uterine cancer, including endometrial cancer. (Endometrial cancer affects the lining inside your uterus.)
However, the American Cancer Society notes that the drug may be helpful for females with either
Most endometrial cancers are stimulated to grow by estrogen. First-line treatment of endometrial cancer is usually surgery that’s done to remove the uterus. The ovaries are often removed as well to reduce estrogen production.
But if these treatments don’t work to treat the endometrial cancer, a hormone therapy may be used to further reduce estrogen in your body. Hormone therapies, such as Arimidex, are
If you have questions about treatment options for uterine cancer, talk with your doctor.
Arimidex for uterine fibroids (off-label use)
Arimidex isn’t FDA approved to treat uterine fibroids. With this condition, you have noncancerous growths in your uterus.
However, Arimidex
If you have questions about using Arimidex for uterine fibroids, talk with your doctor. They can recommend safe and effective treatment options.
Arimidex for breast cancer prevention (off-label use)
Arimidex isn’t FDA approved to prevent breast cancer. However, sometimes it’s used off-label to prevent breast cancer in certain females who have a high risk of the condition.
If you have questions about using Arimidex to prevent breast cancer, talk with your doctor.
Arimidex for bodybuilding (not a legal use)
Arimidex is sometimes used by bodybuilders and other athletes to offset certain side effects of anabolic steroids. However, the FDA has not approved this use, and buying Arimidex for this purpose is illegal. In addition, the World Anti-Doping Agency lists anastrozole as a substance that’s prohibited for use in competitive sports. (Anastrozole is the active ingredient in Arimidex.)
Arimidex and children
Arimidex isn’t FDA approved for use in children.
The drug has been studied in boys ages 11 to 18 years with gynecomastia (breast growth in males). It’s also been studied in girls ages 2 to 9 years with early puberty that’s caused by McCune-Albright syndrome. However, Arimidex wasn’t found to be effective for either of these conditions.
Depending on the type of breast cancer you’re using Arimidex to treat, you might take other drugs with Arimidex.
For example, Arimidex is sometimes taken with targeted therapies to treat advanced breast cancer. (With advanced breast cancer, the cancer has either spread to nearby areas or lymph nodes, called locally advanced breast cancer, or spread to other parts of your body, called metastatic breast cancer.)
Targeted therapies work on specific features of cancer cells. These therapies include drugs such as palbociclib (Ibrance) and ribociclib (Kisqali).
In addition, if you’re at risk of weakened bones with Arimidex treatment, you might take a medication called a bisphosphonate to help protect your bones. Examples of bisphosphonates include alendronate (Fosamax) and risedronate (Actonel).
If you’d like to know more about taking other drugs with Arimidex, talk with your doctor. They can recommend a treatment plan that’s right for you.
Other drugs are available that can treat breast cancer. Some may be a better fit for you than others. If you’re interested in finding an alternative to Arimidex, talk with your doctor. They can tell you about other medications that may work well for you.
Examples of other drugs that may be used to treat breast cancer include:
- hormone therapies other than Arimidex, such as:
- targeted therapies, such as:
- chemotherapy drugs, such as:
- doxorubicin
- epirubicin (Ellence)
- paclitaxel (Abraxane)
- docetaxel (Taxotere)
- capecitabine (Xeloda)
- cyclophosphamide
* These drugs are also used for adjuvant treatment of breast cancer. Adjuvant treatment is given to lower the risk of breast cancer coming back after it’s been treated with surgery.
You may wonder how Arimidex compares with other medications that are prescribed for similar uses. Here we look at how Arimidex and tamoxifen are alike and different.
Ingredients
Arimidex contains the active ingredient anastrozole. Tamoxifen is an active ingredient that’s available in both generic and brand-name forms. (A generic drug is an exact copy of the active ingredient in a brand-name medication.)
Arimidex and tamoxifen are hormone therapies that are used to treat breast cancer. These drugs work by stopping the hormone estrogen from stimulating cancer cells to grow and spread.
Arimidex is a type of hormone therapy called an aromatase inhibitor. It works by stopping estrogen from being made in your body by the aromatase enzyme. (Enzymes are certain proteins that help chemical reactions happen inside your body.)
Tamoxifen is a type of hormone therapy called a selective estrogen receptor modulator (SERM). It works by stopping estrogen from attaching to cancer cells in your body.
Uses
Arimidex is approved to treat breast cancer in females who have gone through menopause. Specifically, Arimidex is used to treat the following types of breast cancer in certain situations:
- lower the risk of early hormone receptor-positive (HR-positive) breast cancer from coming back or spreading after it has already been treated with surgery (called adjuvant treatment)
- first-line treatment (the first treatment prescribed) for locally advanced or metastatic breast cancer that’s either HR-positive or HR-unknown
- locally advanced or metastatic breast cancer that’s come back or spread after treatment with the cancer drug tamoxifen
For details about these uses of Arimidex, see the “Arimidex (anastrozole) uses” section above.
Tamoxifen is approved for use in both males and females. In fact, it can be prescribed for all females, regardless of whether they’ve reached menopause. Tamoxifen is used to:
- lower the risk of early estrogen receptor-positive (ER-positive) breast cancer from coming back or developing in the opposite breast after surgery (called adjuvant treatment)
- treat ER-positive metastatic breast cancer
- lower the risk of invasive breast cancer (cancer that’s developed in the breast tissue or lymph nodes) after surgery and radiation treatment in females with ductal carcinoma in situ (DCIS)*
- help prevent breast cancer in females who have high risk of developing the condition
* With DCIS, which is the earliest form of breast cancer, cancer cells are only found in your milk ducts.
Note: Sex and gender exist on spectrums. Use of the terms “female” and “male” in this article refers to sex assigned at birth.
Drug forms and administration
Arimidex comes as tablets that you take by mouth once per day.
Tamoxifen comes as tablets that you take by mouth either once or twice per day. Tamoxifen tablets used to be sold as the brand-name drug Nolvadex. However, this brand-name drug has been discontinued.
Tamoxifen is also available in a liquid form that’s sold as the brand-name drug Soltamox. This form is also taken by mouth.
Side effects and risks
Arimidex and tamoxifen can cause some similar and some different side effects. Below are examples of these side effects.
Mild side effects
These lists contain examples of mild side effects that can occur with Arimidex, with tamoxifen, or with both drugs (when taken individually).
- Can occur with Arimidex:
- sore throat
- weakness
- carpal tunnel syndrome (a nerve condition that affects your wrist)
- Can occur with tamoxifen:
- vaginal discharge or bleeding
- Can occur with both Arimidex and tamoxifen:
- hot flashes
- peripheral edema (swelling in your legs, ankles, or feet that’s caused by fluid retention)
- lymphedema (buildup of lymphatic fluid in the tissues of your arm, which causes swelling in the area)
- mood changes, such as depression
- fatigue
- dizziness
- pain, such as joint or back pain
- arthritis
- rash
- nausea and vomiting
- insomnia
- headache
- bone pain
Serious side effects
These lists contain examples of serious side effects that can occur with Arimidex, with tamoxifen, or with both drugs (when taken individually).
- Can occur with Arimidex:
- increased cholesterol level
- heart problems
- Can occur with tamoxifen:
- Can occur with both Arimidex and tamoxifen:
- severe allergic reaction
- liver problems, such as hepatitis (liver inflammation)
- skin reactions
- reduced bone mineral density (weakened bones)
* Tamoxifen has a boxed warning for these side effects. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
Effectiveness
Arimidex and tamoxifen have different FDA-approved uses. But they’re both used as adjuvant treatment of early breast cancer and as treatment of advanced breast cancer in females who’ve gone through menopause.
In a clinical trial of females with early breast cancer, 5 years of Arimidex treatment after surgery was more effective than 5 years of tamoxifen treatment after surgery for preventing:
- their cancer from coming back after surgery
- their cancer from spreading to other areas of their body
- their cancer from occurring in their other (unaffected) breast
- death
One study looked at treatment in females with advanced breast cancer. In this study, first-line treatment with Arimidex was more effective than first-line treatment with tamoxifen in slowing down the growth and spread of the cancer. For this study, most of the females had HR-positive cancer. The hormone receptor status wasn’t known in some of the females.
Costs
Arimidex is a brand-name drug. It’s also available in generic form. (A generic drug is an exact copy of the active ingredient in a brand-name medication.)
Tamoxifen is an active ingredient that’s available in both generic and some brand-name forms.
The actual price you’ll pay for either drug depends on your insurance plan, the dosage your doctor prescribes, your location, and the pharmacy you use.
Visit Optum Perks to find coupons and savings for Arimidex and tamoxifen.
You may wonder how Arimidex compares with other medications that are prescribed for similar uses. Here we look at how Arimidex and letrozole are alike and different.
Ingredients
Arimidex contains the active ingredient anastrozole. Letrozole is an active ingredient that’s available in both generic and brand-name forms. (A generic drug is an exact copy of the active ingredient in a brand-name medication.) Letrozole is sold as the brand-name drug Femara.
Arimidex and letrozole are both hormone therapies that are used to treat breast cancer. Hormone therapies for breast cancer work by stopping estrogen from stimulating the cancer to grow and spread. Both of these drugs belong to a class of drugs called aromatase inhibitors.
Uses
Arimidex and letrozole are approved to treat breast cancer in females who have gone through menopause. Specifically, these drugs are used to treat the following types of breast cancer in certain situations:
- lower the risk of early hormone receptor-positive (HR-positive) breast cancer from coming back or spreading after it has already been treated with surgery (called adjuvant treatment)
- first-line treatment (the first treatment prescribed) for locally advanced or metastatic breast cancer that’s either HR-positive or HR-unknown
- locally advanced or metastatic breast cancer that’s come back or spread after treatment with the cancer drug tamoxifen
For details about these uses, see the “Arimidex (anastrozole) uses” section above.
In addition, letrozole is also approved to lower the risk of early HR-positive breast cancer from coming back after surgery that’s followed by 5 years of tamoxifen treatment. Arimidex is used off-label for this purpose. (With off-label use, a drug that’s approved for one purpose is prescribed for another.)
Note: Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.
Drug forms and administration
Both Arimidex and letrozole come as tablets that are taken by mouth once per day.
Side effects and risks
Arimidex and letrozole both contain a type of drug called an aromatase inhibitor. Therefore, these medications can cause very similar side effects. Below are examples of these side effects.
Mild side effects
These lists contain examples of mild side effects that can occur with Arimidex, with letrozole, or with both drugs (when taken individually).
- Can occur with Arimidex:
- sore throat
- back pain
- arthritis
- insomnia
- carpal tunnel syndrome (a nerve condition that affects your wrist)
- lymphedema (buildup of lymphatic fluid in the tissues of your arm, which causes swelling in the area)
- mood changes, such as depression
- Can occur with letrozole:
- no unique mild side effects
- Can occur with both Arimidex and letrozole:
- hot flashes
- weakness
- fatigue
- dizziness
- pain, such as joint or bone pain
- headache
- nausea and vomiting
- rash
- peripheral edema (swelling in your legs, ankles, or feet that’s caused by fluid retention)
- weight gain
Serious side effects
These lists contain examples of serious side effects that can occur with Arimidex, with letrozole, or with both drugs (when taken individually).
- Can occur with Arimidex:
- liver problems, such as hepatitis (liver inflammation)
- skin reactions
- heart problems
- Can occur with letrozole:
- no unique serious side effects
- Can occur with both Arimidex and letrozole:
- severe allergic reaction
- reduced bone mineral density (weakened bones)
- increased cholesterol level
Effectiveness
Arimidex and letrozole are both FDA approved for use in females who’ve gone through menopause. These drugs can be used for adjuvant treatment of early breast cancer and as treatment of advanced breast cancer.
One clinical study found Arimidex and letrozole to be similarly effective for adjuvant treatment of early breast cancer.
In addition, the
Costs
Arimidex is a brand-name drug. It’s also available in generic form. (A generic drug is an exact copy of the active ingredient in a brand-name medication.)
Letrozole is an active ingredient that’s available in both generic and brand-name forms.
The actual price you’ll pay for either drug depends on your insurance plan, your location, and the pharmacy you use.
Visit Optum Perks to find coupons and savings for Arimidex and letrozole.
Here are answers to some frequently asked questions about Arimidex.
How much does Arimidex increase survival?
A
According to this review, taking an aromatase inhibitor, such as Arimidex, for 5 years reduced the risk of dying from breast cancer within the following 5 years by 40%. This means that people taking an aromatase inhibitor for 5 years have a 40% lower risk of death from breast cancer compared with people using no hormone treatment.
If you have questions about survival rates for people taking Arimidex, talk with your doctor. Keep in mind that results of Arimidex treatment may vary from person to person.
What happens when you stop taking Arimidex?
When you stop taking Arimidex, the drug that’s left in your body will be gradually broken down by your liver. How long Arimidex stays in your system can vary from person to person. But most of the drug is usually removed from your body within about 10 days.
While in your body, Arimidex works to lower your estrogen level. This hormone level will stay low for up to 6 days after you’ve stopped taking the drug. This is the period of time until your body starts to gradually begin making estrogen again.
If you had side effects related to low estrogen, such as hot flashes, these should start to lessen as your estrogen level increases.
Stopping Arimidex doesn’t cause withdrawal symptoms. (Withdrawal symptoms are side effects that can happen when you stop taking a drug that your body has become dependent on. With dependence, your body needs the drug to function as usual.) And stopping Arimidex suddenly (sometimes called “stopping cold turkey”) should not cause any problems for you.
If you’ve been taking Arimidex to lower the risk of your breast cancer coming back, clinical trials show that your risk is still lowered for at least 5 years after you stop treatment. (This applies to people who’ve taken Arimidex for about 5 years of treatment.)
If you’re thinking about stopping Arimidex, talk with your doctor. They can discuss with you the risks and benefits of doing so.
How much does Arimidex lower your estrogen?
Arimidex can lower your estrogen level significantly after 24 hours following your dose of the drug. The level will typically be lowered more after you’ve taken Arimidex every day for 2 weeks. Your estrogen level may stay this low for up to 6 days after you stop taking Arimidex.
Will I have any permanent damage after using Arimidex?
It’s not likely that you will. In fact, side effects of Arimidex usually go away once you’ve stopped taking the drug.
However, Arimidex can weaken your bones while you’re taking it. And some females can develop osteoporosis from this. (With osteoporosis, you have thin, weak bones.) You also have an increased risk of breaking a bone with Arimidex treatment. But one clinical trial found that after stopping Arimidex, the risk of breaking a bone was no longer increased.
If you’re concerned about long-term side effects or permanent damage caused by Arimidex, talk with your doctor. They can discuss with you the risks and benefits of using this drug.
Note: Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.
What percentage of people have breast cancer recurrence while they’re taking Arimidex?
Like all drugs, Arimidex doesn’t work for everyone. And this drug is less likely to prevent breast cancer recurrence if your cancer is estrogen receptor-negative (ER-negative). (ER-negative cancer doesn’t need estrogen in order to grow.)
One clinical trial looked at Arimidex as adjuvant treatment for breast cancer in females who were postmenopausal. (For adjuvant treatment, Arimidex is given to lower the risk of the breast cancer coming back or spreading, after it’s already been treated with surgery.)
In this trial, breast cancer did come back in some people. It came back either in the same breast, in the other breast, or in another part of their body.
Over this 5-year study, breast cancer came back in 10.4% of females who took Arimidex. In comparison, breast cancer came back in 12% of females who took the cancer drug tamoxifen for adjuvant treatment.
Out of the females whose breast cancer was hormone receptor-positive (HR-positive),* cancer came back in 8.6% of females who took Arimidex. In comparison, of those with HR-positive breast cancer who took tamoxifen, up to 10.2% had their cancer come back.
* With HR-positive breast cancer, the cancer is stimulated to grow by hormones, including estrogen.
Arimidex is approved to treat certain types of breast cancer in females who’ve gone through menopause.
Note: Sex and gender exist on spectrums. Use of the terms “female” and “male” in this article refers to sex assigned at birth.
What breast cancer is
Breast cancer develops when cells in your breast start to grow and multiply (make more cells) more quickly than usual. With most breast cancers, the abnormal cells are stimulated to grow by the hormone estrogen.
If your breast cancer is stimulated by hormones, such as estrogen, certain tests will show that the cancer cells have receptors (attachment sites) for those hormones. This type of breast cancer is called hormone receptor-positive (HR-positive).
HR-positive cancers can be treated with hormone therapies that lower the estrogen level in your body. And because most breast cancer is HR-positive, hormone therapies are also sometimes used to treat breast cancer with unknown receptor status.
What Arimidex does
Arimidex is a hormone therapy that’s used to treat certain forms of breast cancer. It’s a type of drug called an aromatase inhibitor. Arimidex works by stopping (inhibiting) the action of an enzyme called aromatase. (Enzymes are certain proteins that help chemical reactions happen inside your body.)
The aromatase enzyme makes estrogen out of steroid hormones in your body, such as testosterone. Aromatase is found in various tissues, including your brain, fat, and skin.
Before menopause, estrogen is mainly produced by your ovaries. And just a small amount is made by the aromatase enzyme. But after menopause, your ovaries stop producing estrogen. At that point, the aromatase enzyme is the main way that your body makes estrogen. (And in males, estrogen is also mainly produced by the aromatase enzyme.)
By stopping aromatase from working, Arimidex lowers the amount of estrogen in your body. This helps to stop estrogen from stimulating breast cancer to grow and spread.
How long does it take to work?
Arimidex will start working soon after you begin taking it. But you won’t be able to notice this. Your doctor may order different kinds of tests during your treatment to check whether the drug is working for you.
Alcohol isn’t known to interact with Arimidex. However, if you have certain side effects of Arimidex, drinking alcohol could worsen them. These side effects include headaches, dizziness, nausea, and tiredness.
Drinking large amounts of alcohol while you’re taking Arimidex can increase your risk of osteoporosis (weak, thin bones). Because of this risk, it’s best to avoid drinking large amounts of alcohol during Arimidex treatment.
Alcohol is also known to raise your risk of developing breast cancer. But at this time, it’s not known whether drinking alcohol after you’re diagnosed with breast cancer can make your cancer worse or make it more likely to come back after treatment.
If you drink alcohol and you’re concerned about how this could affect your breast cancer or its treatment, talk with your doctor. They can give you advice on how much alcohol, if any, is safe for you to drink.
Arimidex can interact with several other medications.
Different interactions can cause different effects. For instance, some interactions can interfere with how well a drug works. Other interactions can increase side effects or make them more severe.
Arimidex and other medications
Below are some of the medications that can interact with Arimidex. This section does not list all the drugs that may interact with Arimidex.
Before taking Arimidex, talk with your doctor and pharmacist. Tell them about all prescription, over-the-counter, and other drugs you take. Also tell them about any vitamins, herbs, and supplements you use. Sharing this information can help you avoid potential interactions.
If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.
Arimidex and tamoxifen
Like Arimidex, tamoxifen is a hormone therapy that’s used to treat breast cancer. But taking tamoxifen with Arimidex can lower the amount of Arimidex in your body. This can make Arimidex less effective for you.
Because of this interaction, you should not take tamoxifen with Arimidex. However, if recommended by your doctor, it’s fine to take Arimidex after you’ve finished taking tamoxifen.
Arimidex and drugs that contain estrogen
Taking Arimidex with drugs that contain estrogen could make Arimidex less effective for you. Because of this, you should not take these types of drugs while you’re using Arimidex.
Examples of drugs that contain estrogen include:
- hormone replacement therapy (HRT)
- vaginal estrogen products, such as creams and tablets
- birth control medications, such as pills, patches, and vaginal rings
If you have questions about using medications that contain estrogen with Arimidex, talk with your doctor.
Arimidex and herbs and supplements
There aren’t any herbs or supplements that have been specifically reported to interact with Arimidex. However, you should still check with your doctor or pharmacist before using any of these products while taking Arimidex.
For example, it’s possible that supplements such as red clover or wild yam could make Arimidex less effective. (These supplements are used by some to reduce menopausal symptoms, such as hot flashes.)
This interaction is possible because these supplements contain phytoestrogens, which are weak estrogen-like substances found in certain plants. There isn’t enough information available to say for sure whether taking phytoestrogens can affect your breast cancer treatment.
Be sure to talk with your doctor before taking any herbs or supplements with Arimidex.
Arimidex and foods
There aren’t any foods that are known to interact with Arimidex. Talk with your doctor to find out if there are any foods you should avoid during Arimidex treatment.
Using more than the recommended dosage of Arimidex can lead to serious side effects. Do not use more Arimidex than your doctor recommends.
What to do in case of overdose
If you think you’ve taken too much of this drug, call your doctor. You can also call America’s Poison Centers at 800-222-1222 or use its online tool. But if your symptoms are severe, call 911 or go to the nearest emergency room right away.
You should take Arimidex according to your doctor’s or healthcare professional’s instructions.
When to take
You can take your Arimidex dose at any time of the day. But try to stick with the same time each day.
To help make sure that you don’t miss a dose, try setting a reminder on your phone. A medication timer may be useful, too.
Taking Arimidex with food
You can take Arimidex either with or without food.
Can Arimidex be crushed, split, or chewed?
No, you should not crush, split, or chew Arimidex tablets. Instead, you should swallow them whole. If you have trouble swallowing pills, talk with your doctor or pharmacist.
When you get Arimidex from the pharmacy, the pharmacist will add an expiration date to the label on the bottle.
The expiration date helps guarantee that the medication is effective during this time. The
Storage
How long a medication remains good can depend on many factors, including how and where you store the medication.
Arimidex tablets should be stored at room temperature (68°F to 77°F/20°C to 25°C) in a tightly sealed container. Avoid storing this medication in areas where it could get damp or wet, such as bathrooms.
Disposal
If you no longer need to take Arimidex and have leftover medication, it’s important to dispose of it safely. This helps prevent others, including children and pets, from taking the drug by accident. It also helps keep the drug from harming the environment.
The
As with all medications, the cost of Arimidex can vary.
The actual price you’ll pay depends on your insurance plan and the pharmacy you use.
Your insurance plan may require you to get prior authorization before approving coverage for Arimidex. This means that your doctor and insurance company will need to communicate about your prescription before the insurance company will cover the drug. The insurance company will review the request and let you and your doctor know whether your plan will cover Arimidex.
If you’re not sure whether you’ll need to get prior authorization for Arimidex, contact your insurance company.
Drug coupons
You can visit Optum Perks for price estimates of Arimidex. These estimates are based on the use of Optum Perks coupons. Note: Optum Perks coupons cannot be used with insurance copays or benefits.
Financial and insurance assistance
If you need financial support to pay for Arimidex, or if you need help understanding your insurance coverage, help is available.
AstraZeneca, the manufacturer of Arimidex, offers a program called Arimidex Patient Direct, which can help lower the cost of your prescription. This program also provides support from pharmacists.
For more information and to find out if you’re eligible for support, call 855-250-2483 or visit the program website.
Arimidex hasn’t been studied in pregnant females. In animal studies, the drug did cause harm to fetuses when it was given to pregnant animals. Keep in mind that animal studies don’t always predict what will happen in humans. However, based on how Arimidex works, it could be harmful to a human fetus if taken during pregnancy.
Before starting Arimidex, tell your doctor if you’re pregnant or planning to become pregnant. And see your doctor right away if you get pregnant or think you could be pregnant while you’re taking Arimidex.
If you’re a female who’s able to become pregnant, your doctor will check for pregnancy before having you start Arimidex.
Note: Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.
Arimidex could harm a fetus if taken during pregnancy. If you’re sexually active and you or your partner can become pregnant, talk with your doctor about your birth control needs while you’re using Arimidex.
If you’re able to become pregnant, you should use birth control while taking this drug. And you should continue using birth control for at least 3 weeks after your last dose of Arimidex.
It’s not known whether Arimidex passes into human breast milk, or if it affects how your body makes breast milk. But the drug could be harmful to a child who consumes it in breast milk.
You should not breastfeed while using this drug or for at least 2 weeks after taking your last dose.
If you’re breastfeeding, talk with your doctor before taking Arimidex. They can recommend safe and healthy ways to feed your child.
Before taking Arimidex, talk with your doctor about your health history. Arimidex may not be right for you if you have certain medical conditions or other factors affecting your health. These include:
- Allergy to Arimidex. Do not take Arimidex if you’re allergic to anastrozole (the active ingredient in Arimidex) or to any of the inactive ingredients in Arimidex. If you’re unsure about your medication allergies, talk with your doctor.
- Ischemic heart disease. With this condition, the blood flow to your heart is lower than usual. This is due to narrowed arteries that supply blood to your heart. If you have angina (a type of chest pain) or you’ve ever had a heart attack, taking Arimidex could worsen your heart problems. Talk with your doctor about any heart issues before taking Arimidex. And call your doctor right away if you have new or worsening chest pain, or shortness of breath while you’re taking Arimidex.
- High cholesterol levels. Arimidex can increase your cholesterol level. During Arimidex treatment, you’ll have blood tests to check your cholesterol level. If your level rises too high, your doctor may recommend medication to help lower your cholesterol.
- Osteoporosis. Arimidex can weaken your bones. This can cause new or worsening osteoporosis (weak, thin bones). The drug also increases your risk of breaking a bone. Your doctor may want to measure your bone mineral density while you’re taking Arimidex. If you have osteoporosis, or any risk factors for developing this condition, you may need to take medication to help protect your bones during Arimidex treatment. (Risk factors for osteoporosis include having a family history of osteoporosis, inactivity, smoking, drinking alcohol, and not getting enough calcium or vitamin D.) Talk with your doctor about your risk of bone density loss while you’re taking Arimidex.
- Severe liver problems. Arimidex hasn’t been studied in people with severe liver problems. Though rare, this drug may cause liver problems, such as hepatitis (liver inflammation). Let your doctor know if you’ve had any liver issues before taking Arimidex. Talk with your doctor about whether this drug is right for you.
- Menstruation. If you’re still having periods (menstruating), talk with your doctor before taking Arimidex. The drug is approved for use only by females in postmenopause. (This means you’ve gone through menopause and no longer have periods.) If you’re still having periods, ask your doctor whether treatments other than Arimidex are better choices for you.
- Pregnancy. Arimidex may cause fetal harm if taken during pregnancy. For more information, please see the “Arimidex and pregnancy” section above.
- Breastfeeding. Do not take Arimidex if you are breastfeeding. For more information, please see the “Arimidex and breastfeeding” section above.
For more information about the potential negative effects of Arimidex, see the “Arimidex side effects” section above.
Note: Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.
Disclaimer: Medical News Today 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.
