The standard medicine used for making women grow eggs ( a treatment called ovulation induction) for many years used to be clomid ( clomiphene citrate). A recent alternative to clomid is the new drug called letrozole( Femara). Letrozole, is an aromatase inhibitor, and is now being increasingly used as an alternative to clomid for inducing ovulation.
The problem with clomid is that because of its antiestrogenic activity, it would cause the cervical mucus to dry up; or make the uterine lining thin. This effect would reduce fertility, so that even though ovulation induction was achieved, women would not get pregnant. Letrozole does not have the anti-estrogenic activity which clomid does, so that the uterine lining and cervical mucus with letrozole is often better than it is with clomid.
The dose is 2.5 mg daily for 5 days, starting from Day 3. Aromatase is an enzyme which converts androstendione ( an androgen) to estradiol, and because this action is blocked by letrozole , the estradiol level in the blood drops. The resulting lower estradiol will in turn stimulate the release of increased amounts of pituitary FSH and LH, and thus stimulate ovulation.
Letrozole was first developed as a medicine to treat certain women with breast cancer. It is because letrozole is an antiestrogen and reduces the estradiol level that it is effective in treating patients with estrogen receptor positive breast cancer .
However, the fact that letrozole is used for treating breast cancer causes women a lot of needless worry ! This fact is conspicuously printed in the patient information leaflet with the drug – and women then start worrying that letrozole will cause them to develop breast cancer. They are also very confused as to why the doctor is giving them a drug to treat breast cancer, when what they have is infertility !
Please remember that letrozole is safe and effective. A drug which is used for treating breast cancer will not cause it ! And do remember that one medicine can be used for many different purposes. The use of letrozole for ovulation induction is an off-label use, as it is not officially approved for this purpose, because pharmaceutical companies do not want to spend the money which is needed to get this approval.