LETROZOLE
(brand name Femara)

What is Letrozole?

The new aromatase inhibitor, Letrozole, reversibly, inhibits the enzyme responsible for estrogen biosynthesis. By decreasing the estrogen levels in the body it may release the hypothalamus and/or pituitary from the negative feed back of estrogen on the release of gonadotropins. This will result in an increase in endogenous FSH and LH, which stimulate the development of ovarian follicles. This is similar to the proposed mechanism of action of clomiphene citrate. However, Letrozole may have another peripheral mechanism of action directly in the ovaries. Letrozole is eliminated from the body in a few days after last administration (in contrast to CC which may last up to few months). Also, it does not have a direct antiestrogen action by itself as in CC. So there should be no unwanted peripheral antiestrogen effects on the endometrium, the cervix…etc.

The commercial name of Letrozole is Femara. It is available in 2.5 & 5 mg tablets. It is a drug that was developed to inhibit the estrogen production in postmenopausal women with breast cancer. We are not using it as a chemotherapy drug. It has been tested and tolerated very well when administered continuously for several months.

Who is a candidate for Letrozole?

Patients who meet one or more of the following criteria may be offered the option of trying Letrozole for induction of ovulation:

• Failure to ovulate on clomiphene citrate.

• Ovulation with clomiphene citrate but with very thin endometrium (less than 0.5 cm)

• Ovulation with clomiphene citrate with failure to achieve pregnancy after 6 cycles.

• Severe side effects with clomiphene citrate.


The classical alternative in the above-mentioned conditions would be FSH injections. This option will be discussed with the patient first. Considering the higher expenses and inconvenience of daily injections with possible severe hyperstimulation, Letrozole may be a safe and acceptable drug to try.

What are the possible side effects?

Usually mild in the form of headache, mild gastrointestinal upsets, hot flushes and easy fatigue.

 

Info taken from web:

 

1. I can pitch in some info about Femara. I am currently doing an IUI cycle using it. It does work somewhat similar to Clomid. It suppresses the production of your estrogen, which in turn sends a signal to your brain to produce more FSH, which stimulates follicle maturation and supposedly may improve egg quality. There have not been many studies done on the use of Femara, though. It appears that pregnancy rates in patients on Femara are similar to those on Clomid, even though it does not tend to produce multiple follicles. The upside is that, unlike Clomid, it does not cause a thinning of the uterine lining, which by itself may improve pregnancy rate.