Anastrozole belongs to the group of cancer-fighting medications known as antineoplastics, and specifically to the group of antineoplastics known as nonsteroidal aromatase inhibitors. It fights breast cancer by inactivating an enzyme known as aromatase. This prevents the enzyme from supplying the estrogen that allows certain types of breast cancers to grow.

Anastrozole can be used after surgery to treat postmenopausal people with hormone-receptor-positive early breast cancer. Anastrozole can also be used to treat postmenopausal people with advanced breast cancer.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended dose of anastrozole is 1 mg once daily, at the same time each day, taken with or without food. Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, and it is more than 12 hours until your next dose, take the missed dose and continue with your regular schedule. If it is less than 12 hours until your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

You should keep your tablets in the package they came in and store them at room temperature in a dry place. Keep it out of the reach of children.

Do not use anastrozole if you:

• are allergic to anastrozole or any ingredients of the medication
• are breast-feeding
• are pregnant

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• diarrhea
• hair thinning
• headache
• hot flashes
• loss of appetite
• nausea or vomiting
• pain in muscles, bones, or joints
• skin rash
• tiredness
• trigger finger (condition where one of your fingers gets stuck in a bent position)
• vaginal dryness
• weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• bone fractures
• chest pain
• increased blood pressure
• increased cholesterol levels
• signs of carpal tunnel syndrome (e.g., tingling pain, coldness, and weakness in parts of the hand)
• signs of depression (such as feeling sad, losing interest in things you used to enjoy, weight changes, changes in sleep habits, feelings of guilt or worthlessness, thoughts of suicide)
• signs of osteoporosis (e.g., unusual fractures, bone pain, back pain that is worse when standing or walking)
• symptoms of tendon disorders (e.g., pain, swelling and tenderness around a joint)
• symptoms of tendon tears (e.g., snap or pop when the tear happens, severe pain, swelling)
• tingling or numbness of the skin
• unusual vaginal discharge, itching, or bleeding

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of a heart attack (e.g., tightness or feeling of heaviness in your chest or pain radiating to your arms or shoulders, neck, teeth, jaw, abdomen, or back)
• symptoms of liver problems (e.g., abdominal pain, persistent vomiting, feeling unwell, fever, itching, yellowing of the skin and eyes, dark urine)
• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

There are certain circumstances and medical conditions where this medication is not recommended or should be taken with caution. Make sure your doctor knows about all your medical conditions before you begin therapy.

Bone mineral density: Long-term use of anastrozole may decrease the density of bones, thereby increasing the risk of osteoporosis. Your doctor will order bone mineral density tests periodically while you are taking anastrozole.

Cholesterol: Anastrozole can cause increases in cholesterol and other lipids in the blood. If you are at an increased risk of developing high cholesterol, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Drowsiness/dizziness: Anastrozole may cause dizziness or drowsiness. If you experience either or both of these side effects, you should not drive, use machinery, or perform any other activities that require alertness.

Heart disease: This medication may increase the risk of heart attack or increased blood pressure. If you are at risk for heart disease or high blood pressure, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you experience signs of a heart attack, such as tightness or heaviness in your chest, sudden chest pain spreading to your arms or shoulders, sweating, nausea, or anxiety, seek medical help immediately.

Kidney function: If you have reduced kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: If you have liver disease or reduced liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Muscle and tendon problems: Anastrozole, like other similar medications, can cause joint inflammation and joint, tendon, and muscle pain. Although rare, there is also an increased risk of tendon rupture. Tendons connect muscles to bones. If you experience sudden extreme pain and swelling of a joint, get immediate medical attention.

Pre-menopausal people: You should not use this medication if you have not yet started menopause.

Pregnancy: Although anastrozole has not been studied with pregnant people (it is intended for use only by people who have passed menopause), it is suspected that it could cause serious problems, possibly including miscarriage. Therefore, it should not be used during pregnancy. Tell your doctor immediately if you become pregnant.

Breast-feeding: It is not known whether anastrozole passes into breast milk. Because of the risks associated with this drug, people using this medication should not breast-feed.

Children: This medication is not intended for use by children.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.