Anastrozole is a prescription medication used to treat breast cancer in postmenopausal women. It specifically treats hormone receptor-positive tumors that are fueled by estrogen. Anastrozole belongs to a group of drugs called aromatase inhibitors. These medications work by blocking an enzyme called aromatase that helps your body make estrogen.
Anastrozole is a prescription medicine used:
- in the treatment of early breast cancer:
- after surgery
- in women whose breast cancer is hormone receptor-positive
- for the first treatment of breast cancer that has spread to nearby tissue or lymph nodes (locally advanced) or has spread to other parts of the body (metastatic), in women whose breast cancer is hormone receptor-positive or the hormone receptors are not known
- for treatment of advanced breast cancer, if the cancer has grown, or the disease has spread after tamoxifen therapy
This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.
Anastrozole may cause serious side effects. See the "Anastrozole Precautions" section.
Common side effects in women taking anastrozole include the following:
- hot flashes
- joint pain
- carpal tunnel syndrome (tingling, pain, coldness, weakness in parts of the hand)
- sore throat
- mood changes
- high blood pressure
- nausea and vomiting
- thinning of the hair (hair loss)
- back pain
- sleep problems
- bone pain
- increased cough
- shortness of breath
- lymphedema (build up of lymph fluid in the tissues of your affected arm)
- trigger finger (a condition in which one of your fingers or your thumb catches in a bent position)
This is not a complete list of anastrozole side effects. Ask your doctor or pharmacist for more information.
Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:
- tamoxifen. You should not take anastrozole if you take tamoxifen. Taking anastrozole with tamoxifen may lower the amount of anastrozole in your blood and may cause anastrozole not to work as well.
- estrogen-containing medicines
- hormone replacement therapy
- birth control pills
- estrogen creams
- vaginal rings
- vaginal suppositories
This is not a complete list of anastrozole drug interactions. Ask your doctor or pharmacist for more information.
Serious side effects have been reported with anastrozole including the following:
- heart disease. Women with early breast cancer, who have a history of blockages in heart arteries (ischemic heart disease) and who take anastrozole may have a slight increase in this type of heart disease compared to similar patients who take tamoxifen. Stop taking anastrozole and call your doctor right away if you have chest pain or shortness of breath. These can be symptoms of heart disease.
- osteoporosis (bone softening and weakening). Anastrozole lowers estrogen in your body, which may cause your bones to become softer and weaker. This can increase your chance of fractures, specifically of the spine, hip and wrist. Your doctor may order a test for you called a bone mineral density study before you start taking anastrozole and during treatment with anastrozole as needed.
- increased blood cholesterol (fat in the blood). Your doctor may do blood tests to check your cholesterol while you are taking anastrozole.
- skin reactions. Stop taking anastrozole and call your doctor right away if you get any skin lesions, ulcers, or blisters.
- severe allergic reactions. Get medical help right away if you get:
- swelling of your face, lips, tongue, or throat
- trouble swallowing or breathing
- liver problems. Anastrozole can cause inflammation of your liver and changes in liver function blood tests. Your doctor may check you for this. Stop taking anastrozole and call your doctor right away if you have any of these signs or symptoms of a liver problem:
- a general feeling of not being well
- yellowing of your skin or whites of your eyes
- pain on the right side of your stomach-area (abdomen)
Do not take anastrozole if you:
- are allergic to any ingredient in anastrozole
- are pregnant, think you may be pregnant, or plan to get pregnant
- have not finished menopause (are premenopausal)
- are a man or child
- are taking tamoxifen or estrogen-containing medicines
Medicines can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of anastrozole there are no specific foods that you must exclude from your diet when receiving anastrozole.
Before taking anastrozole, tell your doctor about all your medical conditions, including if you:
- are allergic to any ingredient in anastrozole
- have not finished menopause
- have or had a heart problem
- have a condition called osteoporosis
- have high cholesterol
- are pregnant or breastfeeding
Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements.
Tell your doctor if you are pregnant or plan to become pregnant.
The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.
Anastrozole falls into category X. It has been shown that women taking anastrozole during pregnancy may have babies with problems. There are no situations where the benefits of the medication for the mother outweigh the risks of harm to the baby. These medicines should never be used by pregnant women.
Tell your doctor if you are breastfeeding or are planning to breastfeed.
It is not known if anastrozole crosses into human milk. Because many medications can cross into human milk and because of the possibility for serious adverse reactions in nursing infants with use of this medication, a choice should be made whether to stop nursing or stop the use of this medication. Your doctor and you will decide if the benefits outweigh the risk of using anastrozole.
Take anastrozole exactly as prescribed by your doctor. Keep taking anastrozole for as along as your doctor prescribes it for you.
Anastrozole comes as a tablet to be taken by mouth with or without food. It is usually taken once a day. If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose. Take your next regularly scheduled dose. Do not take two doses at the same time.
Take anastrozole exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.
The recommended dose for anastrozole is one 1 mg tablet taken once a day. For patients with advanced breast cancer, anastrozole should be continued until tumor progression. Anastrozole can be taken with or without food.
If you take too much this medication, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.
If this medication is administered by a healthcare provider in a medical setting, it is unlikely that an overdose will occur. However, if overdose is suspected, seek emergency medical attention.
- Store anastrozole at 68°F to 77°F (20°C to 25°C).
- Keep anastrozole and all medicines out of the reach of children.
You should not take anastrozole if you take tamoxifen. Taking anastrozole with tamoxifen may lower the amount of anastrozole in your blood and may cause anastrozole not to work as well.
Do not take anastrozole if you have not finished menopause (are premenopausal).
Anastrozole can cause an increase in blood cholesterol (fat in the blood). Your doctor may do blood tests to check your cholesterol while you are taking anastrozole.
Breast cancer is cancer that forms in the cells of the breasts. The development of breast cancer is strongly related to the amount of estrogen the breast is exposed to over time. Some women have hormone receptor positive (ER/PR+) breast cancer. Estrogen receptors are proteins found on the surface of cells. Cancer cells grow in response to estrogen binding to these receptors. Anastrozole lowers the amount of estrogen in the blood, limiting the amount of estrogen available to bind to these receptors. This slows or stops the growth of cancer cells.
Hormone receptor testing is done to determine how likely it is that anastrozole will be an effective treatment. Patients who do not have hormone receptor positive breast cancer are not likely to respond to treatment with anastrozole.