Anastrozol

Anastrozol is a non-steroidal aromatase inhibitor used in the treatment of estrogen receptor-positive breast cancer, primarily in postmenopausal women. It is marketed under the brand name Arimidex and as a generic medication. By inhibiting the aromatase enzyme (CYP19) in peripheral tissues, it lowers estrogen production and reduces the growth stimulus for ER-positive tumors.

Anastrozol is indicated as adjuvant therapy for postmenopausal women with early-stage ER-positive breast cancer to reduce recurrence risk, and as treatment for advanced or metastatic ER-positive breast cancer as endocrine therapy. It is not effective in premenopausal women with functioning ovaries unless ovarian estrogen production is suppressed, such as with concomitant ovarian suppression.

The usual dose is 1 mg taken orally once daily, with or without food. In adjuvant therapy, treatment commonly lasts five years, though regimens may vary and therapy continues until disease progression or intolerance.

Common adverse effects include hot flashes, joint or muscle pain (arthralgia/myalgia), fatigue, nausea, and decreased bone mineral density, which can increase the risk of osteoporosis and fractures. Other potential effects are headaches, sweating, edema, and hypertension. Rare liver enzyme elevations and liver injury can occur. Because estrogen suppression can affect lipid profiles and quality of life, monitoring is advised.

Contraindications include pregnancy and breastfeeding. In premenopausal women, anastrozol is generally ineffective unless ovarian function is suppressed. Concurrent use with estrogen-containing therapies should be avoided, and careful sequencing is advised with selective estrogen receptor modulators such as tamoxifen.

Pharmacokinetically, anastrozol is well absorbed orally and has a half-life of about 40–50 hours, with hepatic metabolism and renal/fecal excretion.