Anastrozole

Pronunciation: an-AS-troh-zole.

Generic name
anastrozole
Drug class
Non-steroidal aromatase inhibitor
Form
Tablet, 1 mg
Route
Oral
Legal status
Prescription-only

Availability and supply rules vary by country

Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand

Australia: Arimidex (5) · Full directory

What anastrozole is and how it works

Anastrozole is a prescription-only aromatase inhibitor used to treat hormone-receptor-positive breast cancer in women who have been through the menopause. It works by blocking an enzyme (aromatase) that produces oestrogen outside the ovaries, lowering the oestrogen that can fuel this type of breast cancer's growth. (1) (2)

Take anastrozole exactly as your prescriber directs, usually once a day. Treatment courses, including in the adjuvant (after-surgery) setting, are often planned for around 5 years and are managed by your cancer care team, with regular monitoring.

Mechanism of action: how anastrozole works

Anastrozole is a potent, selective, non-steroidal inhibitor of aromatase, the enzyme responsible for converting androgens to oestrogens in peripheral tissue in postmenopausal women. By lowering circulating oestradiol, it slows the growth of hormone-receptor-positive breast cancer. (1) (4)

What anastrozole is used for

Hormone-receptor-positive breast cancer (early and advanced)

Used for adjuvant (after initial treatment) therapy of early breast cancer, and for advanced or metastatic breast cancer, in postmenopausal women whose cancer is hormone-receptor-positive (or hormone-receptor status unknown for first-line advanced disease). Also used after disease progression on tamoxifen. (1)

Breast cancer risk reduction in postmenopausal women at higher risk

In the United Kingdom, also used for primary prevention (risk reduction) of breast cancer in postmenopausal women identified as being at moderate-to-high risk, based on clinical trial evidence (the IBIS-II study). (2)

Before taking anastrozole

Do not take / not appropriate for

  • Do not take anastrozole if you have had an allergic reaction to it or any of its ingredients. (all countries) (1) (4)
  • Anastrozole is not used in premenopausal women -- it has not been shown to be safe or effective before menopause. (all countries) (2) (4)
  • Anastrozole is not used during pregnancy or while breastfeeding. (all countries) (1) (4)

Tell your clinician about

  • Whether you have been through the menopause, or any uncertainty about your menopausal status.
  • Any history of osteoporosis, low bone density, or fracture risk factors.
  • Any heart or circulation problems, including angina or a prior heart attack.
  • Any severe liver or kidney problems.
  • All other medicines you take, especially tamoxifen or any oestrogen-containing therapy (including some hormone replacement therapy).
(1) (2) (4)

How to take anastrozole

  • Take one 1 mg tablet by mouth once a day, with or without food.
  • Take it at around the same time each day to help you remember.
  • Your prescriber will tell you how long your course of treatment should last -- adjuvant treatment is often planned for around 5 years.
(1) (4)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

If you miss a dose, take it as soon as you remember that day; if it is almost time for your next dose, skip the missed one and continue your regular schedule -- do not take two doses together. Contact your prescriber or pharmacist if you are unsure.

Overdose

Seek emergency medical help immediately if you think you or someone else may have taken too much anastrozole. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Hot flashes and asthenia (weakness/low energy) are very common.

What to notice: Hot flashes and asthenia (weakness/low energy) are very common.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Joint pain, joint stiffness, and arthritis.

What to notice: Joint pain, joint stiffness, and arthritis.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1) (2)

Headache and nausea.

What to notice: Headache and nausea.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (2)

Rash.

What to notice: Rash.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1) (2)

Raised cholesterol.

What to notice: Raised cholesterol.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1) (4)

Insomnia, back pain, and depression.

What to notice: Insomnia, back pain, and depression.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Serious warnings

Bone thinning (osteoporosis) and increased fracture risk — high caution

Symptoms: Often no symptoms until a fracture occurs; back pain or height loss over time can be a sign of a spinal fracture.

Action: Your prescriber will monitor your bone density (for example with a DXA scan) during treatment and may recommend a bone-protecting medicine (such as a bisphosphonate) if you are at higher risk. Report any new bone pain or a fall-related injury promptly. (1) (2) (4)

Signs of a heart or circulation problem — emergency

Symptoms: Chest pain or tightness, sudden shortness of breath, or signs of a stroke (facial drooping, arm weakness, slurred speech).

Action: Seek emergency medical help immediately. Anastrozole has been associated with a higher rate of ischaemic cardiovascular events, particularly in people with pre-existing heart disease. (1) (4)

Signs of a serious allergic reaction — emergency

Symptoms: Swelling of the face, lips, tongue, or throat; difficulty breathing; widespread rash or hives.

Action: Seek emergency medical help immediately -- anaphylaxis, angioedema, and urticaria have been reported with anastrozole. (1)

Interactions

  • Tamoxifen is not used in combination with anastrozole, as it may reduce anastrozole's effectiveness. (1) (2)
  • Oestrogen-containing therapies, including some forms of hormone replacement therapy, may diminish anastrozole's effect and are generally avoided during treatment -- tell your prescriber about any hormone-containing products you use. (1) (2)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Anastrozole is contraindicated in pregnancy -- animal studies showed harm to the developing fetus, and it is only used in postmenopausal women. (1) (2) (3) (4) (5) (6)

Breastfeeding

Anastrozole is contraindicated during breastfeeding; the US label advises not breastfeeding during treatment and for 2 weeks after the final dose. (1) (2) (3) (4) (5) (6)

Children

Not recommended in children -- efficacy has not been established in this age group. (1) (2) (3) (4) (5) (6)

Elderly

No dose change is needed based on age alone; anastrozole is commonly used in older postmenopausal women. (1) (2) (3) (4) (5) (6)

Hepatic_impairment

No dose change is generally needed for mild-to-moderate liver impairment, with monitoring for side effects; severe liver impairment requires your prescriber to carefully weigh potential risks and benefits, as it has not been well studied in this group. (1) (2) (3) (4) (5) (6)

Renal_impairment

No dose change is generally needed for kidney impairment; severe kidney impairment requires your prescriber to carefully weigh potential risks and benefits. (1) (2) (3) (4) (5) (6)

Source_ids

US-DAILYMED-ARIMIDEX-2026,CA-HC-ARIMIDEX-2026,NZ-MEDSAFE-ARIMIDEX-2024 (1) (2) (3) (4) (5) (6)

Monitoring

Before starting

  • Confirmation of postmenopausal status
  • Baseline bone density assessment where risk factors are present
  • Cardiovascular risk assessment
  • Cholesterol level where clinically relevant

During treatment

  • Periodic bone mineral density monitoring, especially if you have osteoporosis risk factors.
  • Monitoring for signs of heart or circulation problems.
  • Monitoring cholesterol levels where clinically relevant.
  • Regular review of continued need for treatment as part of your overall cancer care plan.
(1) (2) (4)

Storage

Store at controlled room temperature, 20-25C (68-77F).

Professional information

Clinician-facing context only, sourced from the current US FDA prescribing information and Health Canada product monograph; verify against the current full label before prescribing.

United States

Indication: Adjuvant, first-line advanced, and post-tamoxifen advanced hormone-receptor-positive breast cancer in postmenopausal women

Dose summary: 1 mg orally once daily, with or without food. No formal renal/hepatic dose adjustment established in the source reviewed; ATAC trial data show increased ischemic cardiovascular events versus tamoxifen (17% vs 10%) in patients with pre-existing ischemic heart disease, and BMD decreases versus baseline.

Renal context: Not specifically established in the source reviewed for this dossier. (1)

Canada

Indication: Hormone-receptor-positive breast cancer, adjuvant setting typically 5 years

Dose summary: 1 mg orally once daily. No dose change necessary for elderly patients, mild-to-moderate hepatic impairment, or renal impairment (monitor for side effects); severe hepatic/renal impairment requires careful risk/benefit assessment. Serious Warnings and Precautions Box: not recommended in premenopausal women; careful risk/benefit assessment in severe hepatic/renal impairment and in osteoporosis/fracture-risk patients. BMD loss in at-risk patients may be mitigated by combining anastrozole with a bisphosphonate (risedronate).

Renal context: No dose change necessary; severe impairment requires risk/benefit assessment. (4)

Mechanism of action

Hepatic guidance

No dose adjustment recommended for mild-to-moderate hepatic impairment based on pharmacokinetic data remaining within the range seen in patients without liver disease; not studied in severe hepatic impairment, requiring individualised risk/benefit assessment.

Overdose note

Limited clinical experience with overdose; general supportive management and monitoring are appropriate, per the source reviewed. (1) (4)

Frequently asked questions

Is anastrozole (Arimidex) available in the US, UK, Europe, Canada, Australia, and New Zealand?

Yes, it is approved and available in all of these regions, as brand-name Arimidex and generic anastrozole. (1) (2) (3) (4) (5) (6)

Does anastrozole have a boxed warning like some other cancer medicines?

No. Anastrozole does not carry a US FDA boxed warning. It does carry real warnings worth knowing about -- bone density loss/fracture risk, a higher rate of certain heart-related events, and raised cholesterol -- which your care team monitors for throughout treatment. (1) (2)

Can I take anastrozole with tamoxifen or hormone replacement therapy?

No. Tamoxifen and oestrogen-containing therapies (including some hormone replacement therapy) are not combined with anastrozole, as they may reduce how well it works. (1) (2)

What is the mechanism of action of anastrozole?

Anastrozole is a potent, selective, non-steroidal inhibitor of aromatase, the enzyme responsible for converting androgens to oestrogens in peripheral tissue in postmenopausal women. By lowering circulating oestradiol, it slows the growth of hormone-receptor-positive breast cancer. (1) (4)

What is the generic name of Anastrozole?

The generic name is anastrozole. (1)

What class of drug is anastrozole?

Anastrozole is classed as: Non-steroidal aromatase inhibitor. (1)

References

  1. ARIMIDEX (anastrozole) tablet -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information, AstraZeneca Pharmaceuticals LP · United States · accessed 2026-07-29 · source 1
  2. Arimidex 1mg Film-Coated Tablet -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- AstraZeneca UK Limited · United Kingdom · accessed 2026-07-29 · source 2
  3. Arimidex (anastrozole) 1mg film-coated tablet -- CHMP assessment report / anastrozole nationally authorised medicinal products listEuropean Medicines Agency (EMA) -- CHMP assessment report and PSUSA nationally-authorised-products list · European Union · accessed 2026-07-29 · source 3
  4. ARIMIDEX (anastrozole) -- Product MonographHealth Canada product monograph, AstraZeneca Canada Inc. · Canada · accessed 2026-07-29 · source 4
  5. ARIMIDEX (anastrozole) 1mg tablets -- ARTG registrationTherapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-29 · source 5
  6. ARIMIDEX Data SheetMedsafe (New Zealand regulator) · New Zealand · accessed 2026-07-29 · source 6

Brand names by country

Single-ingredient anastrozole names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • ARIMIDEX1 mg · ani pharmaceuticals, inc.

United Kingdom

  • Arimidex (2)MHRA licensed emc smpc confirmed · 1 mg · AstraZeneca UK Limited

Canada

  • ARIMIDEX
  • ZINDA-ANASTROZOLE
  • ACH-ANASTROZOLE
  • MED-ANASTROZOLE

Australia

  • Arimidex (5)TGA ARTG registered 1996-12-17 confirmed · 1 mg · AstraZeneca Pty Ltd

New Zealand

  • Arimidex (6)Medsafe approved confirmed · 1 mg · AstraZeneca New Zealand
View brands in additional countries.

European Union

Arimidex / national generic brands (3)

This page provides general reference information about anastrozole and is not a substitute for advice from the prescriber or cancer care team managing your treatment. All dosing and treatment decisions should be made with your prescriber.

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