Each film coated tabletcontains:
Letrozole USP 2.5 mg
Letrozole is a third generation, non-steroidal aromatase inhibitor. It is chemically described as 4,4'-(1H-1,2,4-Triazol-1-ylmethylene) dibenzonitrile.
CLINICAL PHARMACOLOGY Mechanism of Action
Aromatase is the enzyme responsible for converting androgens to estrogens. Letrozole by inhibiting aromatase reduces the production of estrogens. This results in enhanced stimulation of gonadotropin releasing hormone (GnRH) which inturn leads to increased secretion of follicle stimulating hormone (FSH) & luteinizing hormone (LH). The outcome is normal ovarian follicular development & ovulation.
Letrozole is rapidly absorbed after oral administration.Absorption is not affected by the food. The maximum plasmalevels reached about 1 hour after ingestion. Letrozole has a bioavailability of 99.9 %. Plasma protein binding of Letrozole is approximately 60% mainly to albumin (55%). It is metabolized by CPY2A6 and CYP3A4 to inactive carbinol metabolite (4, 4' methanolbisbenzonitrile) which is excreted in urine. The elimination half-life is about40-42 hours
The usual dose is 2.5 mg to be taken for 5 days from day 3 to day 7 of menstrual cycle. Higher doses up to 5 mgmay be used in women who do not get desired results with lower dose.
Letrozole is contraindicated in patients who are hypersensitive to Letrozole, pregnancy, liver dysfunction, abnormaluterine bleeding, uncontrolled thyroid or adrenal dysfunction or in the presence of an organic intracranial lesionsuch as pituitary tumor.
No clinically significant interaction of Letrozole has been reported with cimetidine, warfarin & diazepam.
Clinical trials evaluating ovulation induction with Letrozole have proven that it is well tolerated. The only side effect reported in these trials was flushing. Use of Letrozole is not associated with increased risk of congenital malformations in humans since Letrozole is eliminated from the body before conception owing to its short half life.Also, cardiac anomalies have occurred less frequently in Letrozole group (0.2%) than general population(0.4-1.2%).
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