Letrozole

Introduction

Letrozole (brand name Femara) is an oral aromatase inhibitor approved by the U.S. Food and Drug Administration (FDA) for use in postmenopausal women with hormone receptor-positive breast cancer. It is also used off-label to help people with certain forms of infertility.

Uses For

Letrozole is used to treat: •Hormone receptor-positive breast cancer in postmenopausal women •Certain types of infertility (ovulation induction in women unable to ovulate and Polycystic Ovary Syndrome)

Mechanism of Action

Letrozole works by blocking the aromatase enzyme, which is responsible for converting androgens (male hormones) to estrogens. By blocking the enzyme, the amount of estrogen in the body is decreased. This then helps to slow or stop the growth of certain types of cancer cell that are estrogen-dependent, as well as helping with certain forms of infertility.

How Long Does It Take to Work?

Letrozole usually begins to work within 1-3 weeks of starting treatment.

Absorption

Letrozole is well absorbed after oral administration, with peak plasma concentrations occurring between 2-3 hours after dosing.

Route of Elimination

Letrozole is eliminated primarily by metabolism (via the liver) and is excreted mainly through the kidneys as metabolites.

Dosage

Adult and elderly patients: The recommended dose of Letrozole is 2.5 mg once daily. In the adjutant and extended adjutant setting, treatment with Letrozole should continue for 5 years or until tumor relapse occurs, whichever comes first. In patients with metastatic disease, treatment with Letrozole should continue until tumor progression is evident. No dose adjustment is required for elderly patients.

Patients with hepatic and/or renal impairment: No dosage adjustment is required for patients with hepatic impairment or renal impairment (creatinine clearance =10 mL/min). However, patients with severe hepatic impairment (Child-Pugh score C) should be kept under close supervision.

Children: Not applicable. The recommended dose of letrozole is 2.5mg orally once daily, taken with or without food. The dose may be adjusted based on individual patient response and side effects.

Administration

Letrozole should be taken once daily, with or without food. Patients should take the medication at the same time each day and should not double up doses.

Side Effects

Common side effects of letrozole include: nausea, hot flashes, fatigue, headache, joint pain, insomnia, and weight gain. Patients should contact their doctor if they experience any of these side effects.

Toxicity

Letrozole is generally well tolerated, with few significant adverse effects in most patients. However, overdose with letrozole can lead to serious toxicity. Symptoms of overdose include nausea, vomiting, abdominal pain, and diarrhea.

Precautions

Patients should tell their doctor about all of their medical conditions before taking letrozole in order to minimize risk of side effects. In particular, those with a history of liver problems or kidney problems should be monitored closely.

Interactions

Letrozole may interact with medications in a few different ways. Letrozole can block the action of estrogen in other medications; conversely, certain medications can increase the effect of letrozole. Before taking letrozole, patients should inform their doctor of any other medications they are taking, including both prescription and over-the-counter drugs.

Drug Interactions

Certain medications may interact with letrozole. This includes warfarin, metformin, aminoglutethimide, and voriconazole. Patients should discuss with their doctor before taking any new medications while on letrozole.

Food Interactions

There are no known food-drug interactions associated with the use of letrozole.

Pregnancy Use

Letrozole is not recommended for use by pregnant women.

Lactation Use

Letrozole is not recommended for use by breastfeeding women.

Acute Overdose

It is unknown what symptoms or adverse effects may be caused by an overdose of letrozole. Patients should seek immediate medical attention if they experience any symptoms associated with an overdose.

Contraindications

Letrozole is contraindicated in patients with known hypersensitivity to letrozole or any other component of the medication.

Use Directions

Patients should take letrozole exactly as prescribed by their doctor and should not take more than the recommended amount. Patients should also inform their doctor of any other medications they are taking, and be sure to take the medication exactly as instructed.

Storage Condition

Letrozole should be stored at room temperature away from excessive heat and moisture.

Volume of Distribution

Letrozole has a volume of distribution of approximately 0.3 L/kg.

Half Life

The half-life of letrozole is approximately 2 days.

Clearance

The clearance of letrozole is approximately 0.3 L/hour/kg.

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Some Frequently Asked Questions About Letrozole