Research has been showing that the breast cancer drug Femara (letrozole) may be a better option thanClomid (clomiphene)to improve pregnancy rates in women withpolycystic ovary syndrome (PCOS).PCOS is the leading cause of ovulatory infertility in the United States.
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Dr. Richard Legro, a reproductive endocrinologist at Penn State Hershey Medical Center presented results from his recent NIH-sponsored trial at the 2012 American Association of Reproductive Medicine (ASRM) conference that showed 25% of women treated with letrozole had a live birth compared to 16.8% of women who took Clomid.
Traditionally, Clomid has been the first-line drug of choice to stimulate ovulation in women with PCOS, and it has a high rate of multiple pregnancies and increases exposure to estrogen. Letrozole doesn’t raise estrogen, it has a lower risk of cardiac abnormalities, and a lower multiple pregnancy rate.
What Is Letrozole?
Letrozole is an aromatase inhibitor that prevents the conversion of androgen to estrogen. It is commonly used to treat estrogen-dependent tumors, particularly breast cancer, in peri-menopausal or post-menopausal women.
This medication is approved for treating hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer.
Everything You Need to Know About HER2-Positive vs. HER2-Negative Breast Cancer
Uses
For this reason, some infertility specialists have been using the drug in women who cannot tolerate or who do not respond well to Clomid. Over the past years, it has emerged as the first-line treatment for anovulatory infertility in PCOS.
Dosing
Letrozole comes in 2.5 mg tablets and is taken once a day for five days, usually beginning on day three or day five of themenstrual cycle. You may need monitoring through blood tests and/or ultrasounds to determine when you are approaching ovulation.
Letrozole should be stopped as soon as pregnancy is achieved.
This medication is incompatible with pregnancy and breastfeeding. However, taking this drug before you become pregnant does not increase your risk of having a child with birth defects.
Side Effects
Overall, letrozole is well tolerated. Side effects may include:
5 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Kar S.Current evidence supporting “letrozole” for ovulation induction.J Hum Reprod Sci. 2013;6(2):93-8. doi:10.4103/0974-1208.117166Legro RS, Kunselman AR, Brzyski RG, et al.The Pregnancy in Polycystic Ovary Syndrome II (PPCOS II) trial: rationale and design of a double-blind randomized trial of clomiphene citrate and letrozole for the treatment of infertility in women with polycystic ovary syndrome.Contemp Clin Trials. 2012;33(3):470-81. doi:10.1016/j.cct.2011.12.005Khakwani M, Parveen R, Yousaf S, Tareen AU.Efficacy of letrozole versus clomiphene citrate on ovulation induction in patients with polycystic ovarian syndrome.Pak J Med Sci. 2022 May-Jun;38(5):1155-1158. doi:10.12669/pjms.38.5.5565Bahri Khomami M, Teede HJ, Joham AE, Moran LJ, Piltonen TT, Boyle JA.Clinical management of pregnancy in women with polycystic ovary syndrome: An expert opinion.Clin Endocrinol (Oxf). 2022 Aug;97(2):227-236. doi:10.1111/cen.14723Monnier A.Long-term efficacy and safety of letrozole for the adjuvant treatment of early breast cancer in postmenopausal women: a review.Ther Clin Risk Manag. 2009;5(5):725-38. doi:10.2147/tcrm.s3858Additional ReadingNayereh Ghomian, M.D., Ashraf Khosravi, M.D., and Nezhat Mousavifar, M.D. A Randomized Clinical Trial on Comparing The Cycle Characteristics of Two Different Initiation Days of Letrozole Treatment in Clomiphene Citrate Resistant PCOS Patients in IUI Cycles. Int J Fertil Steril. 2015 Apr-Jun; 9(1): 17–26.
5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Kar S.Current evidence supporting “letrozole” for ovulation induction.J Hum Reprod Sci. 2013;6(2):93-8. doi:10.4103/0974-1208.117166Legro RS, Kunselman AR, Brzyski RG, et al.The Pregnancy in Polycystic Ovary Syndrome II (PPCOS II) trial: rationale and design of a double-blind randomized trial of clomiphene citrate and letrozole for the treatment of infertility in women with polycystic ovary syndrome.Contemp Clin Trials. 2012;33(3):470-81. doi:10.1016/j.cct.2011.12.005Khakwani M, Parveen R, Yousaf S, Tareen AU.Efficacy of letrozole versus clomiphene citrate on ovulation induction in patients with polycystic ovarian syndrome.Pak J Med Sci. 2022 May-Jun;38(5):1155-1158. doi:10.12669/pjms.38.5.5565Bahri Khomami M, Teede HJ, Joham AE, Moran LJ, Piltonen TT, Boyle JA.Clinical management of pregnancy in women with polycystic ovary syndrome: An expert opinion.Clin Endocrinol (Oxf). 2022 Aug;97(2):227-236. doi:10.1111/cen.14723Monnier A.Long-term efficacy and safety of letrozole for the adjuvant treatment of early breast cancer in postmenopausal women: a review.Ther Clin Risk Manag. 2009;5(5):725-38. doi:10.2147/tcrm.s3858Additional ReadingNayereh Ghomian, M.D., Ashraf Khosravi, M.D., and Nezhat Mousavifar, M.D. A Randomized Clinical Trial on Comparing The Cycle Characteristics of Two Different Initiation Days of Letrozole Treatment in Clomiphene Citrate Resistant PCOS Patients in IUI Cycles. Int J Fertil Steril. 2015 Apr-Jun; 9(1): 17–26.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Kar S.Current evidence supporting “letrozole” for ovulation induction.J Hum Reprod Sci. 2013;6(2):93-8. doi:10.4103/0974-1208.117166Legro RS, Kunselman AR, Brzyski RG, et al.The Pregnancy in Polycystic Ovary Syndrome II (PPCOS II) trial: rationale and design of a double-blind randomized trial of clomiphene citrate and letrozole for the treatment of infertility in women with polycystic ovary syndrome.Contemp Clin Trials. 2012;33(3):470-81. doi:10.1016/j.cct.2011.12.005Khakwani M, Parveen R, Yousaf S, Tareen AU.Efficacy of letrozole versus clomiphene citrate on ovulation induction in patients with polycystic ovarian syndrome.Pak J Med Sci. 2022 May-Jun;38(5):1155-1158. doi:10.12669/pjms.38.5.5565Bahri Khomami M, Teede HJ, Joham AE, Moran LJ, Piltonen TT, Boyle JA.Clinical management of pregnancy in women with polycystic ovary syndrome: An expert opinion.Clin Endocrinol (Oxf). 2022 Aug;97(2):227-236. doi:10.1111/cen.14723Monnier A.Long-term efficacy and safety of letrozole for the adjuvant treatment of early breast cancer in postmenopausal women: a review.Ther Clin Risk Manag. 2009;5(5):725-38. doi:10.2147/tcrm.s3858
Kar S.Current evidence supporting “letrozole” for ovulation induction.J Hum Reprod Sci. 2013;6(2):93-8. doi:10.4103/0974-1208.117166
Legro RS, Kunselman AR, Brzyski RG, et al.The Pregnancy in Polycystic Ovary Syndrome II (PPCOS II) trial: rationale and design of a double-blind randomized trial of clomiphene citrate and letrozole for the treatment of infertility in women with polycystic ovary syndrome.Contemp Clin Trials. 2012;33(3):470-81. doi:10.1016/j.cct.2011.12.005
Khakwani M, Parveen R, Yousaf S, Tareen AU.Efficacy of letrozole versus clomiphene citrate on ovulation induction in patients with polycystic ovarian syndrome.Pak J Med Sci. 2022 May-Jun;38(5):1155-1158. doi:10.12669/pjms.38.5.5565
Bahri Khomami M, Teede HJ, Joham AE, Moran LJ, Piltonen TT, Boyle JA.Clinical management of pregnancy in women with polycystic ovary syndrome: An expert opinion.Clin Endocrinol (Oxf). 2022 Aug;97(2):227-236. doi:10.1111/cen.14723
Monnier A.Long-term efficacy and safety of letrozole for the adjuvant treatment of early breast cancer in postmenopausal women: a review.Ther Clin Risk Manag. 2009;5(5):725-38. doi:10.2147/tcrm.s3858
Nayereh Ghomian, M.D., Ashraf Khosravi, M.D., and Nezhat Mousavifar, M.D. A Randomized Clinical Trial on Comparing The Cycle Characteristics of Two Different Initiation Days of Letrozole Treatment in Clomiphene Citrate Resistant PCOS Patients in IUI Cycles. Int J Fertil Steril. 2015 Apr-Jun; 9(1): 17–26.
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