Letrozole is a nonsteroidal aromatase inhibitor. It inhibits the conversion of androgen to estrogen. In contrast to ovariectomy, treatment with letrozole does not lead to an increase in serum FSH. Letrozole selectively inhibits gonadal steroidogenesis but has no significant effect on adrenal mineralocorticoid or glucocorticoid synthesis. Letrozole inhibits the aromatase enzyme by competitively binding to the heme of the cytochrome P450 subunit of the enzyme, resulting in a reduction of estrogen biosynthesis in all tissues. Treatment of women with letrozole significantly lowers serum estrone, estradiol and estrone sulfate and has not been shown to significantly affect the adrenal corticosteroid synthesis, ldosterone synthesis, or synthesis of thyroid hormones.
The recommended dose is one 2.5 mg tablet administered once a day, regardless to meals. In patients with advanced disease, treatment with Letrozole Tablet should be continued until tumor progression is evident. Treatment should be discontinued at tumor relapse. No dose adjustment is required for elderly patients. Patients treated with Letrozole Tablet do not require glucocorticoid or mineralocorticoid replacement therapy.