- Heart disease warning: If you have early breast cancer and a history of blockage in your heart arteries, anastrozole may cause low blood flow to your heart. Call your doctor right away if you have symptoms, which may include:
- shortness of breath
- swelling in your legs and feet
- worsening chest pain
- Low bone density risk: Anastrozole can decrease bone density in your lower spine and hips. Your doctor will monitor your bone mineral density while you’re taking this drug.
- Cholesterol warning: Anastrozole may cause your cholesterol levels to rise. Higher cholesterol levels put you at increased risk of heart disease.
Anastrozole is a prescription drug. It’s available as an oral tablet.
Anastrozole oral tablet is available as the brand-name drug Arimidex and as a generic drug. Generic drugs usually cost less. In some cases, they may not be available in the same strengths or dosage forms as the brand-name version.
This drug may be used with other medications to treat breast cancer.
Anastrozole shouldn’t be used in women who haven’t gone through menopause. If you become pregnant while taking anastrozole, stop taking anastrozole right away.
Why it's used
Anastrozole is used to treat breast cancer. It’s used only in women who have gone through menopause. Specifically, it’s used for:
- treatment of early breast cancer. It’s given to women with hormone receptor-positive or unknown breast cancer after surgery or in addition to other therapies.
- initial or first treatment of breast cancer that has metastasized (spread to other parts of the body). It’s used in women with hormone receptor-positive breast cancer, or women in whom the hormone receptors aren’t known.
- treatment of advanced breast cancer. It’s given when your disease has progressed, even after early response with the cancer drug tamoxifen.
Anastrozole doesn’t work well in women with estrogen receptor-negative breast cancer. It also doesn’t work well in women whose bodies didn’t respond to treatment with tamoxifen.
How it works
Anastrozole belongs to a class of drugs called aromatase inhibitors. They block the production of estrogen, which is a key stimulator of breast cancer. A class of drugs refers to medications that work similarly. They have a similar chemical structure and are often used to treat similar conditions.
In postmenopausal women, an enzyme called aromatase changes hormones called androgens into the hormone estrogen. Many breast cancer tumors grow when estrogen is present. Anastrozole stops aromatase from working. This lowers the amount of estrogen in your body and in the cancer tissue.
Anastrozole oral tablet doesn’t cause drowsiness but it can cause other side effects.
More common side effects
The most common side effects that occur with anastrozole include:
- hot flashes
- bone, joint, and muscle pain or stiffness
- sore throat or cough
- high blood pressure
- nausea or vomiting
- back pain
- skin rash
- trouble sleeping
- swelling of your legs, ankles, or feet
- shortness of breath
- bone fractures
- swelling in your lymph nodes
If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.
Serious side effects
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 the following:
- osteoporosis (bone thinning or weakness). Symptoms may include: pain in your back, neck, or hips
- higher cholesterol levels. This can lead to serious heart problems.
- skin reactions. Symptoms may include:
- abnormal growth on your skin (lesion)
- open sores (ulcers)
- tickling, tingling, pain, coldness, or numbness in parts of your hand
- liver problems. Symptoms may include:
- yellowing of your skin or the whites of your eyes
- pain on the right upper side of your stomach area
- a general feeling of not being well
Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we can not guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
Anastrozole oral tablet can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.
To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.
Examples of drugs that can cause interactions with anastrozole are listed below.
Breast cancer medication
Tamoxifen should not be taken with anastrozole. When these drugs are taking together, the amount of anastrozole in your body can decrease.
Estrogen-containing drugs shouldn’t be taken with this medication. Estrogen can stop anastrozole from working properly. Examples of these drugs include:
- hormone replacement therapy
- birth control pills
- vaginal rings
Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we can not guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.
This drug comes with several warnings.
Anastrozole can cause a severe allergic reaction. Symptoms may include:
- trouble breathing
- swelling of your throat or tongue
If you develop these symptoms, call 911 or go to the nearest emergency room.
Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal.
Contact with drug warning
Don’t share this medication with others, even if they have the same medical condition that you have. This drug could harm them.
Warnings for people with certain health conditions
For people with osteoporosis: Anastrozole lowers the estrogen levels in your body, which may cause your bones to become weak or thin. This could worsen your osteoporosis and further increase your risk for fractures. Your doctor will check your bone mineral density before starting and during treatment with this drug.
For people with high cholesterol: This medication may increase your cholesterol levels. This can raise your risk of serious heart problems. You doctor will check your cholesterol levels while you’re taking anastrozole.
For people with heart disease: If you have a history of blockage in your heart arteries, anastrozole may cause low blood flow to your heart. Talk to your doctor to weigh the risks and benefits of taking this medication to treat your breast cancer.
For people with liver problems: Anastrozole may cause inflammation of your liver. This can worsen liver problems. Your doctor may check your liver function before and during treatment with this drug.
Warnings for certain groups
For pregnant women: Anastrozole is a category X pregnancy drug. Category X drugs should never be used during pregnancy.
Tell your doctor if you’re pregnant or plan to become pregnant. If you become pregnant while taking anastrozole, stop taking this drug right away and call your doctor.
For women who are breastfeeding: It isn’t known if anastrozole passes through breast milk. If it does, it may cause serious effects in a breastfeeding child.
You and your doctor may need to decide if you’ll take anastrozole or breastfeed.
For children: The safety and effectiveness of anastrozole haven’t been established in people younger than 18 years of age.
All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:
- your age
- the condition being treated
- how severe your condition is
- other medical conditions you have
- how you react to the first dose
Dosage for breast cancer
- Form: oral tablet
- Strengths: 1 mg
- Form: oral tablet
- Strengths: 1 mg
Adult dosage (ages 18 years and older)
The typical recommended dosage is one 1-mg tablet taken by mouth once per day.
Child dosage (ages 0–17 years)
This medication hasn’t been studied in children. It shouldn’t be used in people younger than 18 years.
Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we can not guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always talk with your doctor or pharmacist about dosages that are right for you.
Take as directed
Anastrozole is used for long-term treatment. It comes with serious risks if you don’t take it as prescribed.
If you don't take it at all, stop taking it, or don’t take it schedule: Your breast cancer may come back.
If you take too much: Call your doctor or go to the emergency room right away. Taking too much of this drug may cause serious side effects such as severe bleeding, death of tissues, or gastritis.
What to do if you miss a dose: If you forget to take your dose, take it as soon as you remember. If it’s just a few hours before the time for your next dose, then only take one dose at that time.
Never try to catch up by taking two doses at once. This could result in dangerous side effects.
How to tell if the drug is working: Your doctor will do tests to check if your breast cancer growth has slowed down or stopped.
Keep these considerations in mind if your doctor prescribes anastrozole for you.
- Anastrozole can be taken with or without food.
- Don't crush, break, or chew anastrozole tablets. Swallow them whole.
- Store anastrozole at room temperature between 68°F and 77°F (20°C and 25°C).
- Keep it away from high temperatures.
- Don’t store this medication in moist or damp areas, such as bathrooms.
A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.
When traveling with your medication:
- Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
- Don’t worry about airport x-ray machines. They can’t hurt your medication.
- You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled box with you.
- Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.
Before starting and during treatment with anastrozole, your doctor will monitor your:
- heart function, including blood pressure and heart rate
- cholesterol levels
- liver function
- bone density
Your doctor will check to see if your breast cancer growth has decreased or stopped by doing a breast exam.
Not every pharmacy stocks this drug. When filling your prescription, be sure to call ahead to make sure they carry it.
There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.
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 other healthcare professional before taking any medication. The drug information contained here in 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.