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I have heard that femora is a cancer drug. Why do you prescribe it to treat infertility?
Both clomiphene citrate (Clomid), and letrozole (Femora) are oral medications used to stimulate ovulation. Letrozole is emerging as a viable alternative to clomiphene citrate for women undergoing ovulation induction and ovarian stimulation, although no broad scientific studies have established the drug’s efficacy as the first course standard treatment. Several preliminary studies have shown letrozole to be useful, producing few side effects, especially for women whose uterine lining may be thinned out by clomiphene citrate. As to its exact mechanism, letrozole falls in the category of drugs known as nonsteroidal aromatase inhibitors, meaning it is highly specific in suppressing estrogen synthesis. Aromatase is an important enzyme prompting the creation of estrogen. If the body makes less estrogen, FSH level increases, follicular development increases, and ovulation is stimulated. Letrozole was originally developed for breast cancer treatment, as certain types of breast cancer cells slow their growth in response to decreasing estrogen levels. Some time ago, one journal published an article about a study in Canada in which a very limited number of patients showed an increase of neural tube defects in the fetuses of women who had taken letrozole. However, there have been several subsequent larger studies which did not substantiate these findings. Since letrozole does not block the estrogen receptors, it is less effective than clomiphene citrate in preventing LH from surging. Therefore, on rare occasions, premature ovulation can occur, which is why we monitor our patients taking letrozole more frequently. We have also observed that clomiphene citrate works better for our younger patients, but we do not have conclusive data to support this yet. Generally, clomiphene citrate is used for women who are freezing embryos, whereas letrozole is used for older women who are doing fresh embryo transfers. At New Hope Fertility Center, we evaluate each patient’s individual needs and circumstances and choose medications accordingly. Letrozole has shown to be particularly helpful for a subset of women whose endometrial lining may become thin while taking clomiphene citrate. As an anti-estrogen, clomiphene citrate can limit the development of the endometrial lining, which we believe makes it more difficult for an embryo to implant. For reasons that aren’t quite yet clear, letrozole appears less likely to affect the uterine lining. Furthermore, letrozole has a short life span in the body, whereas clomiphene citrate can last for 4-6 weeks following an oral dose. At New Hope Fertility Center, we are pleased with the results seen so far with letrozole and we look forward to seeing the outcome of studies that are underway to further assess its efficacy as standard treatment.
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