Vexal-A Mechanism of Action

Pharmacologic Classification: Antineoplastic (Aromatase Inhibitor). ATC code: L02B G03.
Pharmacology: Pharmacodynamics: Mechanism of action: Many breast cancers have estrogen receptors and growth of these tumors can be stimulated by estrogen. In postmenopausal women, the principal source of circulating estrogen (primarily estradiol) is conversion of adrenally generated androstenedione to estrone by aromatase in peripheral tissues with further conversion of estrone to estradiol. Many breast cancers also contain aromatase. Treatment of breast cancers included efforts to decrease oestrogen levels. Anastrozole is a potent and highly selective non-steroidal aromatase inhibitor. As with other aromatase inhibitors, Anastrazole lowers oestrogen levels in postmenopausal women by inhibiting conversion of adrenally-generated androstenedione (adrenal androgens) to estrone by aromatase in peripheral tissues. Estrone is subsequently converted to estradiol. Adrenally generated androstenedione is the chief source of circulating estrogen in postmenopausal women. Reducing circulating estradiol levels has been shown to produce a beneficial effect in women with breast cancer.
Pharmacokinetics: Anastrozole is rapidly and almost completely absorbed from the gastrointestinal tract after oral doses, with peak plasma concentrations within about 2 hours. Food decreases the rate of absorption, though this is not considered clinically significant. Anastrozole is 40% bound to plasma proteins. It is metabolised in the liver, and excreted in urine, chiefly as metabolites. The terminal plasma elimination half-life is about 40 to 50 hours, and steady-state concentrations are achieved after about 7 days in patients receiving once-daily doses.