Last reviewed 2026-04-20 · How we verify

Arimidex (anastrozole)

Anastrozole selectively inhibits aromatase enzyme, suppressing estrogen biosynthesis in postmenopausal breast cancer.

Anastrozole is a selective non-steroidal aromatase inhibitor indicated for adjuvant and first-line treatment of hormone receptor-positive breast cancer in postmenopausal women, and for advanced disease following tamoxifen progression. It significantly lowers serum estradiol with a 50-hour half-life and linear pharmacokinetics over 1-20 mg dose range. Key risks include hypersensitivity reactions and contraindication with tamoxifen or estrogen-containing products, with minimal cytochrome P450 interactions at therapeutic doses. The drug demonstrates sustained efficacy with steady-state levels achieved within 7 days of once-daily dosing.

At a glance

Mechanism of action

The growth of many breast cancers is stimulated or maintained by estrogens. In postmenopausal women, estrogens are mainly derived from the action of the aromatase enzyme, which converts adrenal androgens (primarily androstenedione and testosterone) to estrone and estradiol. Anastrozole is a selective non-steroidal aromatase inhibitor that suppresses estrogen biosynthesis in peripheral tissues and cancer tissue by specifically inhibiting the aromatase enzyme. It significantly lowers serum estradiol concentrations and has no detectable effect on formation of adrenal corticosteroids or aldosterone.

Approved indications

• Adjuvant treatment of early breast cancer
• First-line treatment of advanced breast cancer
• Second-line treatment of advanced breast cancer

Common side effects

• Hot flush
• Asthenia
• Constipation
• Nausea
• Arthralgia
• Fatigue
• Hypertension
• Insomnia
• Urinary tract infection
• Decreased appetite
• Headache
• Vertigo

Drug interactions

• Tamoxifen
• Estrogen-containing products
• Warfarin
• Cytochrome P450 substrates

Key clinical trials

• A Randomized Phase III Trial Comparing 16 to 18 Weeks of Neoadjuvant Exemestane (25 mg Daily), Letrozole (2.5 mg), or Anastrozole (1 mg) in Postmenopausal Women With Clinical Stage II and III Estrogen (Phase 3)
• NCT00437853 (NA)
• An Open Label Phase II Study of the Efficacy and Safety of Abemaciclib, a Cyclin Dependent Kinase (CDK4/6) Inhibitor in Selected Patients With Recurrent Ovarian or Endometrial Cancer (Phase 2)
• A Prospective, Randomized, Multicentre, Comparative and Open-label Study on Hepatotoxicity of ARIMIDEX Compared With Tamoxifen in Adjuvant Therapy in Postmenopausal Women With Hormone Receptor+ Early (Phase 4)
• CB-103 Plus NSAI In Luminal Advanced Breast Cancer: CAILA Study (Phase 2)
• Androgen Therapy for Management of Estrogen/Progesterone Receptor Negative ER(-)PR(-) Metastatic Breast Cancer, Phase II Study (Phase 2)
• A Study of Neoadjuvant SHR6390 in Combination With Anastrozole, Pyrotinib, and Trastuzumab in Patients With ER-Positive, HER2-Positive Breast Cancer. (Phase 2)
• Bevacizumab Plus Paclitaxel Optimization Study With Interventional Maintenance Endocrine Therapy in Advanced or Metastatic ER-positive HER2-negative Breast Cancer -BOOSTER Trial, a Multicenter Randomi (Phase 2)

Primary sources

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