Products
Letrozole is commercially available in the form of film-coated tablets (Femara, generic). It has been approved in many countries since 1997.
Structure and properties
Letrozole (C17H11N5, Mr = 285.3 g/mol) is a nonsteroidal aromatase inhibitor. It exists as a white to yellowish crystalline powder that is nearly odorless and virtually insoluble in water. Letrozole is a triazole derivative.
Effects
Letrozole (ATC L02BG04) has antitumor and antiproliferative properties. It inhibits estrogen-dependent breast cancer growth. The effects are due to inhibition of the enzyme aromatase, which converts androgens (androstenedione, testosterone) to the estrogens estrone and estradiol. The enzyme is found in postmenopausal women in peripheral tissues and in the tumor itself (fat, muscle, liver, breast). Letrozole has a long half-life of up to four days.
Indications
For the treatment of breast cancer in postmenopausal women.
Dosage
According to the SmPC. Tablets are taken daily at the same time of day, regardless of meals.
Abuse
Letrozole can be abused as a doping agent and for bodybuilding. It is prohibited during and outside of athletic competition.
Contraindications
- Hypersensitivity
- Premenopause
- Pregnancy, lactation
Full precautions can be found in the drug label.
Interactions
Letrozole is a substrate of CYP3A4 and CYP2A6 and corresponding drug-drug interactions are possible. It should not be combined with estrogens.
Adverse effects
Adverse effects are largely due to reduced estrogen levels. The most common possible adverse effects include:
- Hot flashes, sweating
- Hypercholesterolemia
- Fatigue, weakness, feeling sick.
- Joint pain
