PRODUCT DETAILS: For oral use only
PRODUCT SPECIFICATIONS: Letrozole is a nonsteroidal inhibitor of estrogen
synthesis with antineoplastic activity. As a third-generation aromatase inhibitor,
Letrozole selectively and reversibly inhibits aromatase, which may result in
growth inhibition of estrogen-dependent breast cancer cells.
Aromatase, a cytochrome P-450 enzyme localized to the endoplasmic reticulum
of the cell and found in many tissues including those of the premenopausal
ovary, liver, and breast, catalyzes the aromatization of androstenedione and
testosterone into estrone and estradiol, the final step in estrogen biosynthesis.
Estrogens are produced by the conversion of androgens through the activity of
the aromatase enzyme. Letrozole blocks production of estrogens in this way by
competitive, reversible binding to the heme of its cytochrome P450 unit. The
action is specific, and letrozole does not reduce production of mineralo- or
corticosteroids. In contrast, the antiestrogenic action of tamoxifen, the major
medical therapy prior to the arrival of aromatase inhibitors, is due to its
interfering with the estrogen receptor, rather than inhibiting estrogen production.
Letrozole is approved by the United States Food and Drug Administration (FDA)
for the treatment of local or metastatic breast cancer that is hormone receptor
positive or has an unknown receptor status in postmenopausal women. Side
effects include signs and symptoms of hypoestrogenism. There is concern that
long term use may lead to osteoporosis, which is why prescriptions of Letrozole
are often accompanied by prescriptions of osteoporosis-fighting medication
such as Fosamax.
Letrozole has shown to reduce estrogen levels by 98 percent while raising
The anti-estrogen action of letrozole is preferred by athletes and bodybuilders
for use during a steroid cycle to reduce bloating due to excess water retention
and prevent the formation of gynecomastia related breast tissue that is a side
effect of some anabolic steroids. Usage above 2.5 mg/day is known to
potentially temporarily kill sex drive. Above 5mg/day for extended periods may
cause kidney problems.
Letrozole has also been shown to delay the fusing of the growth plates in
adolescents. This may boost the effectiveness of growth hormone, and thus
Letrozole is used to treat adolescents and children with short stature.