anastrozole

Anastrozole is a non-steroidal aromatase inhibitor used in the treatment of hormone receptor-positive breast cancer in postmenopausal women. It works by reversibly inhibiting aromatase (CYP19A1), the enzyme that converts androgens to estrogen in peripheral tissues, thereby lowering circulating estrogen levels and reducing stimulation of estrogen-dependent tumor growth.

Medical uses include adjuvant therapy for postmenopausal women with early-stage, hormone receptor-positive breast cancer following surgery, and treatment of advanced or metastatic hormone receptor-positive breast cancer in postmenopausal patients. It is not approved for use in premenopausal women unless ovarian suppression is also employed. Anastrozole may be used in specific cases of male breast cancer, though data are more limited.

Administration and pharmacokinetics: The usual dose is 1 mg taken orally once daily, with or without food. It has good oral bioavailability and a long half-life, leading to steady-state concentrations within one to two weeks. It is primarily metabolized in the liver and excreted via feces and urine. Drug interactions can occur with strong CYP3A4 inhibitors or inducers, so concomitant medications should be reviewed.

Safety considerations: Common adverse effects include hot flashes, fatigue, and joint pain (arthralgia or myalgia). Long-term estrogen depletion can lead to decreased bone mineral density and an increased risk of fractures; bone health monitoring and preventive measures are often recommended. Other possible effects include nausea, edema, and lipid changes. Unlike tamoxifen, anastrozole generally has a lower risk of endometrial cancer. It is contraindicated in pregnancy. Liver disease and significant hepatic impairment require caution. Regular monitoring and individualized assessment are advised to balance benefit and risk.