Approximately 2 to 5 percent of pregnant women will develop gestational diabetes mellitus, leading to a significant increase in maternal and neonatal morbidity and mortality. In the past, the first-line therapy for gestational diabetes after failure of diet control was insulin. In one study, researchers found that glyburide (Micronase) was as clinically effective as insulin in treating patients with gestational diabetes. Despite these results, and that recent expert opinion has recommended glyburide as an alternative treatment, only 13 percent of physicians in a 2003 study reported using this medication as first-line therapy. Jacobson and associates evaluated the use of glyburide versus insulin in the treatment of women with gestational diabetes mellitus that has been unresponsive to diet therapy.

A retrospective chart audit of women with gestational diabetes who required medication for control was performed for two years before the introduction of a glyburide protocol and for two years after the protocol was used. The participants were women with singleton pregnancies diagnosed with gestational diabetes between 12 and 34 weeks of gestation and who met the criteria on a three-hour glucose tolerance test established by the National Diabetes Data Group. Women were excluded from the study if their fasting blood glucose level was more than 140 mg per dL (7.77 mmol per L). All of the participants were enrolled in a major prepaid group model managed care organization and were provided with nutritional counseling and instruction on glucose self-monitoring. Patients treated with glyburide were started at a dosage of 2.5 mg daily with their morning meal. If glycemic control was not adequate at the end of one week, the dosage was doubled to 5 mg daily, then increased by 5 mg daily until the patient reached the maximum dosage of 20 mg daily. Patients not controlled on this dosage were changed to insulin therapy. Major outcomes included maternal and neonatal complications.

There were 268 women who met the inclusion criteria and were treated with insulin therapy and 236 who were treated with the glyburide protocol. No significant differences were noted in age, nulliparity, or diabetes risk factors between the groups. Women in the insulin group were more likely to identify themselves as white, had a higher mean body mass index, and had a higher mean fasting glucose level on their glucose tolerance test. More women in the glyburide group attained their mean fasting and postprandial glucose goals than in the insulin group. There were no significant differences in birth weights, macrosomia, or rates of cesarean delivery between the two groups. The neonates in the glyburide treatment group were more likely to receive phototherapy, and the women had a higher incidence of preeclampsia.

The authors conclude that glyburide is at least as effective as insulin therapy in treating gestational diabetes in women with fasting blood glucose levels of 140 mg per dL or less and who fail diet therapy. They add that larger studies are needed to assess some of the less common complications.