Metformin: historical overview

Metformin is a logical treatment for women with gestational diabetes mellitus, but randomized trials to assess the efficacy and safety of its use for this condition are lacking. We randomly assigned 751 women with gestational diabetes mellitus at 20 to 33 weeks of gestation to open treatment with metformin (with supplemental insulin if required) or insulin. The primary outcome was a composite of neonatal hypoglycemia, respiratory distress, need for phototherapy, birth trauma, 5-minute Apgar score less than 7, or prematurity. The trial was designed to rule out a 33% increase (from 30% to 40%) in this composite outcome in infants of women treated with metformin as compared with those treated with insulin. Secondary outcomes included neonatal anthropometric measurements, maternal glycemic control, maternal hypertensive complications, postpartum glucose tolerance, and acceptability of treatment. Of the 363 women assigned to metformin, 92.6% continued to receive metformin until delivery and 46.3% received supplemental insulin. The rate of the primary composite outcome was 32.0% in the group assigned to metformin and 32.2% in the insulin group (relative risk, 0.99 [corrected]; 95% confidence interval, 0.80 [corrected] to 1.23 [corrected]). More women in the metformin group than in the insulin group stated that they would choose to receive their assigned treatment again (76.6% vs. 27.2%, P<0.001). The rates of other secondary outcomes did not differ significantly between the groups. There were no serious adverse events associated with the use of metformin. In women with gestational diabetes mellitus, metformin (alone or with supplemental insulin) is not associated with increased perinatal complications as compared with insulin. The women preferred metformin to insulin treatment. (Australian New Zealand Clinical Trials Registry number, 12605000311651.). Copyright 2008 Massachusetts Medical Society.

Sulfonylurea drugs have been the only oral therapy available for patients with non-insulin-dependent diabetes mellitus (NIDDM) in the United States. Recently, however, metformin has been approved for the treatment of NIDDM. We performed two large, randomized, parallel-group, double-blind, controlled studies in which metformin or another treatment was given for 29 weeks to moderately obese patients with NIDDM whose diabetes was inadequately controlled by diet (protocol 1: metformin vs. placebo; 289 patients), or diet plus glyburide (protocol 2: metformin and glyburide vs. metformin vs. glyburide; 632 patients). To determine efficacy we measured plasma glucose (while the patients were fasting and after the oral administration of glucose), lactate, lipids, insulin, and glycosylated hemoglobin before, during, and at the end of the study. In protocol 1, at the end of the study the 143 patients in the metformin group, as compared with the 146 patients in the placebo group, had lower mean (+/- SE) fasting plasma glucose concentrations (189 +/- 5 vs. 244 +/- 6 mg per deciliter [10.6 +/- 0.3 vs. 13.7 +/- 0.3 mmol per liter], P < 0.001) and glycosylated hemoglobin values (7.1 +/- 0.1 percent vs. 8.6 +/- 0.2 percent, P < 0.001). In protocol 2, the 213 patients given metformin and glyburide, as compared with the 210 patients treated with glyburide alone, had lower mean fasting plasma glucose concentrations (187 +/- 4 vs. 261 +/- 4 mg per deciliter [10.5 +/- 0.2 vs. 14.6 +/- 0.2 mmol per liter], P < 0.001) and glycosylated hemoglobin values (7.1 +/- 0.1 percent vs. 8.7 +/- 0.1 percent, P < 0.001). The effect of metformin alone was similar to that of glyburide alone. Eighteen percent of the patients given metformin and glyburide had symptoms compatible with hypoglycemia, as compared with 3 percent in the glyburide group and 2 percent in the metformin group. In both protocols the patients given metformin had statistically significant decreases in plasma total and low-density lipoprotein cholesterol and triglyceride concentrations, whereas the values in the respective control groups did not change. There were no significant changes in fasting plasma lactate concentrations in any of the groups. Metformin monotherapy and combination therapy with metformin and sulfonylurea are well tolerated and improve glycemic control and lipid concentrations in patients with NIDDM whose diabetes is poorly controlled with diet or sulfonylurea therapy alone.