- Adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer.
- Extended adjuvant treatment of early breast cancer in postmenopausal women who have received 5 years of adjuvant tamoxifen therapy.
- First-line treatment of postmenopausal women with hormone receptor positive or hormone receptor unknown locally advanced or metastatic breast cancer.
- Treatment of advanced breast cancer in postmenopausal women with disease progression following antiestrogen therapy.
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.
A pharmacokinetic interaction study with cimetidine & warfarin showed no clinically significant effect on Letrozole pharmacokinetics. In in-vitro experiments, Letrozole & diazepam showed no significant inhibition in the metabolism of each other. Coadministration of Letrozole and tamoxifen 20 mg daily resulted in a reduction of Letrozole plasma levels of 38% on average. Clinical experience in the second-line breast cancer pivotal trials indicates that the therapeutic effect of Letrozole therapy is not impaired if Letrozole is administered immediately after tamoxifen.
Letrozole may cause fetal harm when administered to a pregnant woman and offers no clinical benefit to premenopausal women with breast cancer. Letrozole is contraindicated in women who are or may become pregnant. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus.
Letrozole is generally well tolerated. The observed adverse reactions are mild or moderate in nature including hot flashes, night sweats, weight increase, nausea, vaginal bleeding & irritation, endometrial proliferation disorders etc.
Pregnancy Category D. It is not known if Letrozole is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Letrozole is administered to a nursing woman.
Since fatigue and dizziness have been observed with the use of Letrozole and somnolence was uncommonly reported, caution is advised when driving or using machinery.
Isolated cases of overdosage with Letrozole have been reported. No specific treatment for overdosage is known; treatment should be symptomatic and supportive.
No dosage adjustment is required for patients with renal impairment if creatinine clearance is 10 ml/min.
Hepatic Impairment: No dosage adjustment is recommended for patients with mild to moderate hepatic impairment. The dose of Letrozole in patients with cirrhosis and severe hepatic dysfunction should be reduced by 50%. The recommended dose for such patients is 2.5 mg administered every other day.
Pediatric Use: The safety and effectiveness in pediatric patients have not been established.
Store in a cool and dry place protected from light and moisture.