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Anastrozole

Hormone Management
ArimidexAIAromatase Inhibitor

Overview

Anastrozole is a synthetic compound classified as a non-steroidal aromatase inhibitor. It is not produced endogenously but is synthesized for therapeutic use. Chemically, it belongs to the class of triazole derivatives. Anastrozole is primarily used in the management of hormone-related conditions, particularly in the treatment of breast cancer in postmenopausal women. Researchers have found that it plays a crucial role in reducing estrogen levels by inhibiting the aromatase enzyme, which is responsible for the conversion of androgens to estrogens. This reduction in estrogen levels is beneficial in slowing the growth of estrogen-dependent tumors. The primary mechanism of action of anastrozole involves the inhibition of the aromatase enzyme, which is a key component in the biosynthesis of estrogens. By blocking this enzyme, anastrozole effectively reduces circulating estrogen levels, thereby decreasing the stimulation of estrogen receptors in estrogen-sensitive tissues. This action is critical in the therapeutic management of estrogen receptor-positive breast cancer. Pharmacokinetically, anastrozole has an elimination half-life of approximately 50 hours, allowing for once-daily dosing. It is well absorbed orally, with a bioavailability of around 83%. The drug is extensively metabolized in the liver, with metabolites excreted primarily in the urine. Clinically, anastrozole is widely used in the treatment of hormone receptor-positive breast cancer in postmenopausal women. It is approved by regulatory agencies such as the FDA and is considered a standard treatment option. Researchers have observed its efficacy in reducing the risk of cancer recurrence. Anastrozole is generally well-tolerated, although it may cause side effects such as hot flashes and joint pain. It is available by prescription and is not classified as a controlled substance.

Mechanism of Action

Anastrozole acts by inhibiting the aromatase enzyme, which converts androgens to estrogens. This inhibition leads to a significant reduction in circulating estrogen levels, thereby decreasing estrogen receptor activation in estrogen-sensitive tissues.

Molecular Data

FormulaC17H19N5
Molecular Weight293.4 g/mol
CAS Number120511-73-1
PubChem CID2187

Half-Life & Pharmacokinetics

OralApproximately 50 hours

Anastrozole is primarily administered orally, with good bioavailability and a long half-life supporting once-daily dosing.

Storage

Temperature

Store at room temperature (15-30°C)

Light

Protect from light

Form

Stable in tablet form for extended periods

Notes

Keep in original packaging to protect from moisture

Solubility

Anastrozole is poorly soluble in water but soluble in organic solvents such as ethanol.

Legal Status

🇩🇪DE

Prescription only (verschreibungspflichtig), not a controlled substance under BtMG.

🇺🇸US

FDA approved for breast cancer treatment, prescription required.

🇦🇺AU

TGA Schedule 4 (prescription only medicine).

🇬🇧UK

Prescription only medicine (POM) under MHRA regulations.

Legal status information is provided for general reference only and may not reflect the most current regulatory changes. Always verify with official government sources before making any decisions.

7 Research Publications

Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer.

Human

Lancet (London, England)

Researchers found that anastrozole, an aromatase inhibitor, significantly improved disease-free survival and reduced the risk of cancer recurrence compared to tamoxifen in postmenopausal women with localized hormone-receptor-positive breast cancer. They also observed that anastrozole had fewer side effects overall, although some patients experienced increased joint pain and fractures.

  • Anastrozole led to fewer cancer recurrences than tamoxifen.
  • Patients on anastrozole experienced fewer side effects, particularly gynecological issues.
  • Anastrozole reduced the occurrence of distant metastases and contralateral breast cancers.
PubMed

The Combination of Aromatase Inhibitors and GH Treatment for Idiopathic Short Stature in Male Adolescents.

Human

The Journal of clinical endocrinology and metabolism · 2025

Researchers found that combining anastrozole, a type of aromatase inhibitor, with growth hormone treatment significantly increased adult height in adolescent boys with idiopathic short stature. They observed that this combination had fewer side effects compared to other treatments, suggesting it may be a more effective option for these patients.

  • Anastrozole combined with growth hormone led to the greatest increase in adult height.
  • The treatment was associated with fewer adverse reactions compared to other combinations.
  • All monitored health indicators returned to normal after stopping treatment.
PubMed

Potent Cell-Cycle Inhibition and Upregulation of Immune Response with Abemaciclib and Anastrozole in neoMONARCH, Phase II Neoadjuvant Study in HR

Human

Clinical cancer research : an official journal of the American Association for Cancer Research · 2020

Researchers observed that combining abemaciclib with anastrozole significantly reduced cell growth in postmenopausal women with certain types of breast cancer compared to using anastrozole alone. After two weeks of treatment, a higher percentage of patients experienced complete cell-cycle arrest, indicating the combination therapy's effectiveness.

  • Abemaciclib combined with anastrozole led to a significant decrease in cell growth.
  • 58% to 68% of patients achieved complete cell-cycle arrest with the combination therapy.
  • The treatment showed biological and clinical activity with manageable side effects.
PubMed

Randomized Trial of Aromatase Inhibitors, Growth Hormone, or Combination in Pubertal Boys with Idiopathic, Short Stature.

Human

The Journal of clinical endocrinology and metabolism · 2016

Researchers found that combining aromatase inhibitors with growth hormone led to greater height increases in pubertal boys with idiopathic short stature compared to using either treatment alone. After 24-36 months, boys receiving the combination therapy grew the most, while all treatments showed a strong safety profile.

  • Combination therapy (AI/GH) resulted in the highest height gain of +22.5 cm.
  • All treatment groups had similar safety outcomes and bone health measures.
  • Aromatase inhibitors affected hormone levels differently, with letrozole showing higher testosterone and lower estradiol than anastrozole.
PubMed

Effect of anastrozole and tamoxifen as adjuvant treatment for early-stage breast cancer: 10-year analysis of the ATAC trial.

Human

The Lancet. Oncology · 2010

Researchers found that anastrozole is more effective than tamoxifen for treating early-stage breast cancer in postmenopausal women, showing better disease-free survival and longer times to recurrence. While anastrozole was associated with more fractures during treatment, it had fewer serious side effects overall compared to tamoxifen.

  • Anastrozole improved disease-free survival compared to tamoxifen.
  • Patients on anastrozole had longer times before cancer recurrence.
  • Serious side effects were less common with anastrozole than tamoxifen.
PubMed

Anastrozole.

Review

Expert opinion on drug safety · 2010

Researchers observed that anastrozole, a medication used for treating hormone receptor-positive breast cancer, is more effective than tamoxifen in postmenopausal women. The review highlights how anastrozole works, its safety compared to tamoxifen, and ongoing research in this area. Adverse effects of anastrozole are also discussed.

  • Anastrozole is more effective than tamoxifen for hormone receptor-positive breast cancer.
  • The review covers the drug's mechanism and safety profile.
  • Ongoing research is exploring further applications of anastrozole.
PubMed

Anastrozole alone or in combination with tamoxifen versus tamoxifen alone for adjuvant treatment of postmenopausal women with early breast cancer: first results of the ATAC randomised trial.

Human

Lancet (London, England) · 2002

Researchers found that anastrozole, when used alone, improved disease-free survival in postmenopausal women with hormone-sensitive early breast cancer compared to tamoxifen. They also observed that anastrozole had fewer severe side effects, such as endometrial cancer and blood clots, while tamoxifen was better tolerated for joint and bone issues. Overall, anastrozole appears to be a more effective and better-tolerated option for these patients.

  • Anastrozole improved disease-free survival at 3 years compared to tamoxifen.
  • Anastrozole had significantly fewer severe side effects than tamoxifen.
  • Tamoxifen was better tolerated for musculoskeletal disorders and fractures.
PubMed

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This page is for informational and research purposes only. All information is based on published scientific literature. Nothing on this page constitutes medical advice or replaces consultation with a qualified healthcare professional.