What Is Anastrozole? Uses, Dosage, and What You Need to Know in 2026

If your doctor has prescribed anastrozole — or you're researching it before your next appointment — you've come to the right place. This guide explains everything you need to know about anastrozole in plain English: what it is, who it's for, how it works, how to take it, and what to watch out for.

What Is Anastrozole?

Anastrozole is a prescription medication used primarily to treat hormone receptor-positive (HR+) breast cancer in postmenopausal women. It is also known by the brand name

Arimidex, though generic versions are now widely available and far less expensive. Anastrozole belongs to a class of drugs called aromatase inhibitors.

Anastrozole works by blocking an enzyme called aromatase, which the body uses to convert male hormones (androgens) into estrogen. By reducing estrogen levels, anastrozole can slow or stop the growth of breast cancers that need estrogen to grow.

What Is Anastrozole Used For?

Anastrozole has three FDA-approved indications, all related to breast cancer in postmenopausal women:

Adjuvant treatment for early HR-positive breast cancer: Taken for 5 years after surgery to reduce the risk of breast cancer coming back.

First-line treatment for advanced or metastatic breast cancer: Used when breast cancer has spread and the tumor is HR-positive or HR-unknown.

Second-line treatment after tamoxifen failure: For women whose cancer has continued to grow even after tamoxifen treatment.

Anastrozole is also used off-label for breast cancer chemoprevention in high-risk women, and occasionally for other estrogen-driven conditions like endometriosis.

Who Should NOT Take Anastrozole?

Anastrozole is not appropriate for everyone. You should not take anastrozole if you:

Have not yet gone through menopause (premenopausal women — the drug is not effective and is potentially harmful)

Are pregnant or may become pregnant (anastrozole can harm a developing baby)

Are currently taking tamoxifen (the combination reduces anastrozole's effectiveness and should be avoided)

Are taking estrogen-containing products like hormone replacement therapy, birth control pills, or estrogen creams (these can counteract anastrozole)

Are allergic to anastrozole or any of its ingredients

How to Take Anastrozole

Dose: 1 mg once daily — one small tablet per day

With or without food: Anastrozole can be taken with or without food, at any time of day. Take it at the same time each day for consistency.

Duration: For early breast cancer, typically 5 years; in node-positive disease, up to 10 years. For metastatic breast cancer, continue as long as it's working and tolerated.

Missed dose: Take it as soon as you remember unless it's almost time for your next dose. Don't double up. Never stop taking anastrozole without talking to your oncologist.

Is Anastrozole the Same as Arimidex?

Yes. Arimidex is the brand name for anastrozole, made by AstraZeneca. Anastrozole is the generic version, available from multiple manufacturers. Both contain the same active ingredient at the same 1 mg dose. Generic anastrozole is FDA-approved and clinically equivalent to Arimidex — and dramatically less expensive. A 30-day supply of generic anastrozole with a discount coupon can cost as little as $5–$15.

Key Things to Know During Treatment

Get a DEXA scan to check bone density before starting and periodically during treatment

Tell your doctor about ALL medications, including vitamins, supplements, and herbal products

Cholesterol levels should be monitored during anastrozole therapy

Report any bone fractures, chest pain, or liver symptoms to your doctor immediately

How Does Anastrozole Work?

Curious about the science? Read our detailed explanation of how anastrozole works at the molecular level. And if you're struggling to fill your prescription, medfinder can help you find a pharmacy near you that has it in stock.