Clinical Drug Experience Knowledgebase

The Effect of Metformin Added to Clomiphene Citrate on Pregnancy Rates in Hyperandrogenic, Chronic Oligoovulatory or Anovulatory Women: A Randomized Trial

Women with polycystic ovary syndrome (PCOS), defined as chronic oligoovulation or anovulation and hyperandrogenism, are primarily treated with clomiphene citrate as first line therapy if they desire pregnancy. However, women with PCOS have lower than expected pregnancy rates in response to clomiphene citrate. Approximately 20% of women with PCOS are resistant to clomiphene citrate. Subjects with chronic oligoovulation or anovulation and hyperandrogenism will ovulate 80% of the time, but pregnancy occurs in only 40%. The ideal initial treatment regimen for women with PCOS who desire pregnancy has not been determined.

Metformin (Glucophage; Bristol-Myers Squibb, Princeton, NJ) is an insulin sensitizer and lowers serum insulin and androgen levels. Numerous case studies, case series, retrospective studies, and non-placebo controlled prospective studies, have suggested an improvement in insulin sensitivity, spontaneous menses, ovulatory response and pregnancies when metformin was given alone or prior to initiation of ovulation inducing agents in women with chronic anovulation and hyperandrogenism.

However, there has been conflicting evidence in the literature regarding the effect of metformin alone or in combination with ovulation inducing agents regarding ovulation and pregnancy rates in prospective, randomized trials. Therefore, it remains unknown if the use of metformin plus clomiphene citrate in non-selected, infertility patients with PCOS improves ovulation and pregnancy rates compared to the use of clomiphene citrate alone.

Women with a history of infertility and diagnosed with hyperandrogenic, oligoovulatory or anovulatory cycles as the sole etiology for their infertility were randomized to receive clomiphene citrate 50 mg days 5-9, plus metformin 500 mg three times daily versus clomiphene plus placebo. The dose of clomiphene was increased up to a maximum dose of 250 mg in a step-wise fashion until ovulation was confirmed with an ovulation predictor kit. Once ovulation was confirmed the subjects continued the ovulatory dose of clomiphene for 6 ovulatory cycles or until conception. Metformin or placebo was started on cycle day one and discontinued 8 days after the LH surge and/or by cycle day 21. A positive HCG, ovulation rates and pregnancy outcome were the outcome measures.