Letrozole 2.5 mg Excipients: lactose monohydrate 50 mg, sodium carboxymethyl starch 2.5 mg, colloidal silicon dioxide 500 mcg, microcrystalline cellulose 28 mg, crospovidone 4 mg, corn starch pregelatinised 11.5 mg, magnesium stearate 1 mg. Film coating composition: opadray Y 1-7000 (hypromellose, titanium dioxide, macrogol (polyethylene glycol)) 3.73 mg, iron oxide yellow dye 270 mcg. Pharmacological action Antitumour drug, an inhibitor of estrogen synthesis. Letrozol has anti-estrogenic effect, selectively inhibits aromatase (enzyme of estrogen synthesis) by highly specific competitive binding to the subunit of this enzyme – heme of cytochrome P450. It blocks estrogen synthesis in both peripheral and tumour tissues. In postmenopausal women, estrogens are formed mainly with the participation of the aromatase enzyme, which converts androgens synthesised in the adrenal glands (primarily androstenedione and testosterone) into estrone and estradiol. Daily administration of Letrozole in a daily dose of 0.1-5 mg leads to a decrease in plasma concentrations of estradiol, estrone and estrone sulfate by 75-95% of the initial content. Suppression of estrogen synthesis is maintained throughout the treatment period. When using Letrozole in the dose range from 0.1 to 5 mg, no disturbance of steroid hormone synthesis in the adrenal glands is observed, the test with ACTH does not reveal any disturbance of aldosterone or cortisol synthesis. Additional prescription of glucocorticoids and mineralocorticoids is not required. Blockade of estrogen biosynthesis does not lead to accumulation of androgens, which are precursors of estrogens. Against the background of Letrozole administration no changes in plasma concentrations of LH and FSH, changes in thyroid function, changes in lipid profile, increased incidence of myocardial infarction and stroke were observed. Against the background of Letrozole treatment the frequency of osteoporosis increases to a small extent (6.9% compared to 5.5% on placebo background). However, the incidence of bone fractures in patients receiving Letrozole does not differ from that in healthy people of the same age. Adjuvant therapy with Letrozole in early stages of breast cancer reduces the risk of recurrences, increases 5-year disease-free survival, reduces the risk of secondary tumours. Extended adjuvant therapy with Letrozole reduces the risk of recurrence by 42%. A significant advantage in disease-free survival in the letrozole group was observed regardless of lymph node involvement.