What Is Anastrozole?
Anastrozole is a nonsteroidal aromatase inhibitor used as hormone therapy, particularly in the treatment of certain hormone receptor-positive breast cancers. It works by reducing the body's production of estrogen, which can help slow or prevent the growth of cancers that depend on estrogen. Arimidex is a well-known brand of anastrozole, and generic anastrozole 1 mg tablets are also available. Anastrozole is a form of hormone therapy, not chemotherapy or a steroid. It is most commonly used in people who have gone through menopause because most estrogen production after menopause occurs through conversion of other hormones by the aromatase enzyme. In premenopausal patients, anastrozole may sometimes be used under specialist supervision alongside treatment that suppresses ovarian estrogen production.
Anastrozole Uses
Approved anastrozole uses commonly include:
Additional treatment for hormone receptor-positive early breast cancer after surgery or other primary treatment
First-line treatment for certain locally advanced or metastatic breast cancers after menopause
Treatment of advanced breast cancer that has progressed after tamoxifen
Specialists may also use it to reduce breast-cancer risk in selected postmenopausal patients or for particular cases of male breast cancer. Indications vary by country.
Benefits of Anastrozole
Anastrozole lowers estrogen levels in the body, which can help slow the growth of hormone-sensitive breast cancer and reduce the risk of the disease returning after initial treatment in appropriate patients. It may be used as part of treatment for early-stage breast cancer or for certain cases of advanced disease, depending on the individual's circumstances. The potential benefit of anastrozole depends on factors such as hormone receptor status, cancer stage, previous treatments, menopausal status, and individual recurrence risk. Treatment decisions should therefore be made with an oncology team based on the patient's specific diagnosis and treatment plan.
How Does Anastrozole Work?
After menopause, the body produces much of its estrogen through a process in which the aromatase enzyme converts other hormones into estrogen in tissues such as fat and muscle. Anastrozole works by blocking aromatase, thereby reducing estrogen production in the body. Lower estrogen levels can help slow the growth of hormone-sensitive breast cancer cells. Depending on the diagnosis and treatment plan, anastrozole may be prescribed after surgery, radiotherapy, chemotherapy, or another hormone treatment to reduce the risk of recurrence or help control advanced disease.
Anastrozole Dosage and How to Take It
The usual labelled anastrozole dosage for adults is one 1 mg tablet once daily, taken with or without food and preferably at approximately the same time each day. For early breast cancer, hormone therapy with anastrozole is commonly planned for around five years, although the duration may be shorter, longer, or involve switching to another endocrine therapy depending on the individual's cancer characteristics, previous treatment, recurrence risk, and specialist recommendations. Take anastrozole consistently as prescribed and do not change the dose, pause treatment, or stop taking it without discussing the decision with your oncology or specialist team.
Anastrozole Side Effects
Common anastrozole side effects include hot flushes, joint pain or stiffness, muscle or bone pain, tiredness, headache, nausea, sleep problems, low mood, vaginal dryness, mild hair thinning and swelling of the hands or feet.
Long-term estrogen reduction can decrease bone density and raise fracture risk. Cholesterol may also increase, so both may be monitored.
Seek prompt medical help for:
Facial or throat swelling, hives or difficulty breathing
A severe, blistering or peeling rash
Yellow skin or eyes, dark urine or severe upper-abdominal pain
New chest pain or symptoms suggesting a heart problem
A new fracture or severe persistent bone pain
What to Avoid When Taking Anastrozole?
People searching “What to avoid when taking anastrozole?” should focus on medicines. Official guidance requires no special diet, and tablets may be taken with or without food.
Avoid or check with the oncology team before using:
Tamoxifen, because using both together provides no added benefit and lowers anastrozole exposure
Estrogen-containing hormone replacement therapy
Estrogen-containing birth-control pills, creams, vaginal rings or suppositories
Unreviewed herbal remedies, hormone supplements or bodybuilding products
Alcohol has no established direct interaction but may worsen hot flushes or dizziness. Discuss supplements with the treatment team.
Who Should Avoid Taking Anastrozole?
Anastrozole is not appropriate for everyone. It should generally be avoided in people with a known allergy to anastrozole or any of its ingredients. It is also contraindicated during pregnancy or when pregnancy is possible, because lowering estrogen can potentially harm a developing fetus. Anastrozole is generally not recommended during breastfeeding, as it may interfere with estrogen production and its effects on a nursing infant are not adequately established.
Anastrozole is primarily used in people who have gone through menopause. Premenopausal patients should not take anastrozole alone because their ovaries continue to produce estrogen; if an aromatase inhibitor is appropriate, it is generally used with specialist-directed ovarian suppression. Anastrozole is also not routinely used in children or adolescents, and its safety and effectiveness for pediatric use have not been established.
Anastrozole Drug Interactions
Before starting anastrozole, provide your oncology team with a complete list of prescription medicines, over-the-counter drugs, vitamins, and supplements you take. Tamoxifen can interfere with the intended effect of anastrozole and generally should not be used at the same time unless specifically directed as part of a specialist treatment plan. Estrogen-containing medicines or hormone products may also counteract the estrogen-lowering effects of anastrozole and should be discussed with your oncology team before use.
Do not start, stop, or change other cancer medicines while taking anastrozole without medical advice. Your oncology team can review potential interactions and determine whether any medicines need to be avoided, adjusted, or taken at a different time.
Storage Instructions
Keep anastrozole tablets in their original packaging at the room temperature specified on the product label. Protect the tablets from excessive moisture, heat, and direct sunlight, and keep them out of reach of children. Do not use tablets that are expired, damaged, or have been stored outside the recommended conditions. Follow the product label or pharmacist's instructions for the safe disposal of unused or expired tablets.