Anastrozole (Arimidex) — Clinical FAQs

Question 1

What is Anastrozole FDA-approved to treat?

Accepted Answer

Anastrozole is FDA-approved for the following oncology indications: 1. Adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer 2. First-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor-unknown locally advanced or metastatic breast cancer 3. Treatment of advanced breast cancer in postmenopausal women with disease progression following tamoxifen therapy.

Question 2

How does Anastrozole work (mechanism of action)?

Accepted Answer

Anastrozole is a potent, highly selective non-steroidal aromatase inhibitor (type II; reversible competitive inhibitor) that inhibits the enzyme aromatase (CYP19A1), which catalyzes the conversion of androgens (androstenedione, testosterone) to estrogens (estrone, estradiol) in peripheral tissues including adipose, muscle, liver, skin, and breast tumor tissue. At the approved dose of 1 mg/day, anastrozole suppresses circulating estradiol by greater than 85% in postmenopausal women, profoundly reducing estrogenic stimulation of hormone receptor-positive breast cancer. Unlike the steroidal aromatase inactivator exemestane, anastrozole binds competitively and reversibly. Because anastrozole does not suppress adrenal androgen synthesis or the hypothalamic-pituitary-gonadal axis, premenopausal women can compensate by upregulating ovarian estrogen production via increased gonadotropin secretion — rendering anastrozole ineffective as monotherapy in premenopausal women without concurrent confirmed ovarian suppression.

Question 3

How is Anastrozole administered?

Accepted Answer

Anastrozole is administered Oral (PO). Administer anastrozole 1 mg orally once daily, with or without food; no clinically significant food effect.

Question 4

What are the most common side effects of Anastrozole?

Accepted Answer

The most commonly reported side effects of Anastrozole (≥10% incidence) include: Arthralgia and joint stiffness (20–35%; leading cause of treatment discontinuation), Myalgia, Hot flashes / vasomotor symptoms, Fatigue, Mood changes / depression and others (13 total). Consult your oncologist for complete prescribing information.

Question 5

Is Anastrozole safe during pregnancy?

Accepted Answer

Anastrozole pregnancy safety: Category X — Anastrozole is contraindicated in pregnant women. Profound estrogen deprivation is embryolethal and causes severe developmental defects. Females of reproductive potential must use effective non-hormonal contraception during therapy and for at least 3 weeks after the final dose.. Oncologists should review the complete prescribing information and discuss reproductive risks with patients before initiating therapy.

Anastrozole — Drug Monograph

Mechanism of Action

FDA Indications

Common Side Effects

Clinical Pearl

Related Therapies & Mechanisms