Letrozole is being used commonly as an infertility treatment. Letrozole is a recent addition to the drugs being used for fertility treatment. Fertility drugs are used often in infertility treatments. There are two situations in which fertility drugs may be useful. First, these drugs can be used to induce an egg to develop and be released in women who are not ovulating on their own. This is known as ovulation induction. Fertility drugs can also be used to increase the chances of pregnancy in women who are already ovulating. This is known as superovulation.
In many fertility centers, clomiphene citrate (Clomid, Serophene) has been the drug of first choice for either ovulation induction or superovulation for many years. In general, it has been a relatively effective medication. However, clomiphene citrate lasts for a long time in the body and may therefore have an adverse effect on the cervical mucus and uterine lining. Some groups of patients, such as women with PCOS – polycystic ovary syndrome, do not respond well to clomiphene citrate. The Pregnancy in Polycystic Ovary Syndrome (PPCOS I) study found that over 6 months time, 1 in 4 PCOS patients never had a single documented ovulation. The cumulative live birth rate was only 23% over the 6 months. One reason theorized for the lower pregnancy rate with clomid is an adverse effect on the uterine lining.
Another group of fertility drugs which are administered as injections are called gonadotropins (Gonal F, Follistim). The gonadotropins are very efficient at inducing ovulation and have higher pregnancy rates than clomiphene citrate. However, gonadotropins are much more expensive than clomiphene citrate and the injectable route is uncomfortable for patients to administer and inconvenient. The risk for multiple pregnancies is also much higher with gonadotropins.
Letrozole is a medication that has been widely used in women with breast cancer. It is sold under the trade name Femara. Letrozole belongs to a class of medications known as aromatase inhibitors. Aromatase is an enzyme that is responsible for the production of estrogen in the body. Letrozole works by inhibiting aromatase thereby suppressing estrogen production. Clomiphene citrate, on the other hand, blocks estrogen receptors. In both cases, the result is that the pituitary gland produces more of the hormones needed to stimulate the ovaries. These hormones, FSH and LH, can cause the development of ovulation in women who are anovulatory or increase the number of eggs developing in the ovaries of women who already ovulate. As a result, several studies have now been published using letrozole as a fertility drug.