Penn State College of Medicine’s nationwide study has shown that Letrozole resulted in higher birth rates in women with polycystic ovary syndrome (PCOS) than the current preferred infertility treatment drug, Clomiphine citrate.

Letrozole blocks estrogen production, while Clomiphine citrate stimulates ovulation.

Funded by Eunice Kennedy Shriver National Institute of Child Health and Development and the National Center for Advancing Translational Sciences, the research compared Letrozole and Clomiphine in 750 infertile women with PCOS between 18 and 40 years old who wanted to conceive.

In this study, women were randomly assigned to either Clomiphene or Letrozole and took the medications for up to five cycles, with increasing dosage each cycle.

The group of women who received Letrozole had 27.5% of live births, while the group of women who received Clomiphene had 19.1% of live births. When compared with Clomiphene, Letrozole showed higher ovulation rates at each monthly visit.

In addition, fewer twin pregnancies occurred in the women who took Letrozole, with 3.9% on Letrozole and 6.9% on Clomiphene.

“The group of women who received Letrozole had 27.5% of live births.”

Clomiphene showed significantly higher incidence of hot flashes and Letrozole showed significantly higher incidence of fatigue and dizziness.

Birth defects were rare and rates were similar between the two drugs, comparable to those from studies of women who conceive without treatment.

According to Penn State College of Medicine, further research is required with a larger number of infants to clarify the safety of Letrozole.

Penn State Hershey Obstetrics and Gynecology professor and lead author Richard Legro said: “It’s only 22% successful with up to six cycles of treatment in producing a successful birth, it has a high multiple-pregnancy rate in comparison to unassisted conception, and it has side effects including hot flashes and mood changes.”

The study results were reported in the New England Journal of Medicine.

Image: Ball-and-stick model of the Letrozole molecule. Photo: courtesy of MindZiper.