Antineoplastic agent, an inhibitor of the synthesis of estrogens. Letrozole has an antiestrogenic effect, selectively inhibits aromatase (an enzyme for the synthesis of estrogens) by highly competitive binding to the subunit of this enzyme, the heme cytochrome P450. It blocks the synthesis of estrogens in both peripheral and tumor tissues.
In postmenopausal women, estrogens are formed predominantly with the participation of the aromatase enzyme, which converts androgen-synthesized androgen (primarily androstenedione and testosterone) into estrone and estradiol.
Daily intake of Letrozole in a daily dose of 0.1-5 mg leads to a decrease in the concentration of estradiol, estrone and estrone sulfate in blood plasma by 75-95% of the original content. Suppression of the synthesis of estrogens is maintained throughout the treatment period.
The drug is taken orally, regardless of food intake.
The recommended dose of Letrozole is 2.5 mg 1 time / day, daily, long-term (for 5 years or until relapse).
As an extended adjuvant therapy treatment should last for 4 years (no longer than 5 years).
If signs of disease progression appear, Letrozole should be stopped.
In patients with last-stage disease or metastatic tumor, treatment with Letrozole should be continued until tumor progression is indicated.
In elderly patients, correction of the dose of Letrozole is not required
– endocrine status characteristic of the reproductive period;
– the period of lactation (breastfeeding);
– Children’s age (effectiveness and safety for children not established);
– Hypersensitivity to the components of the drug.
With caution , the drug should be used with a deficiency of lactase, lactase intolerance, glucose-galactose malabsorption.
There is no data on the use of Letrozole in patients with QC <30 mL / min (prior to prescribing such a patient, the ratio between potential risk and the expected effect of treatment should be carefully weighed).