Ovulation Induction; Letrozol
Tags: Infertility Treatment Ovulation Induction Letrozole
Letrozole - More Information!
Letrozole has been used for over a decade as an alternative to clomiphene for ovulation induction agent. In spite of growing enthusiasm for this medication for infertility treatment in the U.S., FDA has not yet approved it for this use. Clinicians continue to accumulate favorable experience with letrozole as new publications address issues of efficacy, safety, and appropropriate use become clarified. Many questions remain regarding letrozole including the following:
In patients who achieve successful ovulation with letrozole, does it achieve successful pregnancy more frequently than the gold standard oral ovulation medication, clomiphene citrate (Clomid)?
If letrozole is a better option for ovulation induction, is it superior for all infertility patients or just in selected types of patients?
What are the physiologic reasons for its superiority?
Does letrozol achieve successful ovulation more or less frequently than Clomid?
Are there long term risks to the mother or fetus related to letrozole use?
Is the rate of twinning with letrozole higher, lower, or the same as
Is reduced endometrial thickness associated with letrozole use?
Some of the questions listed above have been addressed in earlier blog posts. A recent paper presented at the annual meeting of the European Society of Human Reproduction and Embryology, specifically addresses the question of whether patients with polycystic ovarian syndrome might do better with letrozole compared to Clomid. This paper compared letrozole to Clomid in polycystic ovarian syndrome patients and found that letrozole did offer an improved pregnancy rate compared with Clomid. The pregnancy rate with letrozole was 61.2% with letrozole vs.43% with clomiphene. There was also a trend toward more live births with letrozole compared to clomiphene (48.8% vs. 35.1%). There were no significant differences in the miscarriage rates, multiple birth rates, pre-term births, endometrial thickness or congenital malformations.
The authors of this paper suggest that it is time to seriously consider moving to letrozole as a first choice for infertile polycystic ovarian syndrome patients. Additional large randomized controlled trials are needed before we should begin using letrozole as the first line medication for ovulation induction in patients with polycystic ovarian syndrome. It is also worth noting that a significant percentage of patients initially treated with letrozole failed to respond with successful ovulation. Many of these patients did respond favorably to clomiphene when they were switched to that side of the treatment protocol.