Arimidex® is a highly selective non-steroidal aromatase inhibitor, an enzyme that, in postmenopausal women, converts androstenedione into peripheral tissues to estrone and then to estradiol. In postmenopausal women, Arimidex® at a daily dose of 1 mg causes a decrease in the level of estradiol by 80%.
Arimidex® does not possess progestogen, androgenic and estrogenic activity. Arimidex® in daily doses up to 10 mg does not have an effect on the secretion of cortisol and aldosterone, therefore, when using Arimidex®, no substitution corticosteroids are required.
Effect on bone mineral density
It has been shown that in patients with hormone-positive early postmenopausal breast cancer who are taking Arimidex®, changes in the bone system can be prevented in accordance with the standards established to treat patients with a certain risk of fractures. Thus, the advantage of Arimidex ® in combination with bisphosphonates (in comparison with Arimidex ® only) in patients with an average and high risk of fracture was demonstrated after 12 months in terms of bone mineral density, structural changes in bone tissue and markers of bone resorption. Moreover, in the low-risk group, there was no change in the mineral bone density index against the background of therapy with one preparation of Arimidex® and supporting treatment with vitamin D and calcium.
When therapy with Arimidex ®, including when taken in combination with bisphosphonates, no changes in the level of lipids in the plasma were detected.
Absorption of anastrozole is fast, the maximum concentration in the plasma is reached within 2 hours after ingestion (on an empty stomach). Food slightly reduces the rate of absorption, but not its degree and does not lead to a clinically significant effect on the equilibrium concentration of the drug in the plasma with a single daily dose of Arimidex ®. After 7 days of taking the drug, approximately 90-95% of the equilibrium concentration of anastrozole in plasma is reached. There is no information on the dependence of pharmacokinetic parameters of anastrozole on time or dose. The pharmacokinetics of anastrozole does not depend on the age of postmenopausal women.
Connection with blood plasma proteins – 40%.
Anastrozole is withdrawn slowly, the half-life from the plasma is 40-50 hours. Extensively metabolized in postmenopausal women. Less than 10% of the dose is excreted unchanged in urine within 72 hours after taking the drug.
Anastrozole metabolism is carried out by N-dealkylation, hydroxylation and glucuronization. Metabolites are excreted mainly with urine. Triazole, the main metabolite, determined in plasma, does not inhibit aromatase.
The clearance of anastrozole after oral administration with liver cirrhosis or renal dysfunction does not change.