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Metformin prevented diabetes a substantial 25% after withdrawal. The benefits of metformin in preventing diabetes appear to persist in some patients after the drug has been discontinued, according to a report in the April issue of Diabetes Care. In the Diabetes Prevention Program (DPP), metformin significantly reduced (by 31%) the risk of diabetes in patients with impaired glucose tolerance, the authors explain, but whether these effects were transient or sustained was not determined. The Diabetes Prevention Program Research Group repeated the oral glucose tolerance test 1 to 2 weeks after discontinuation of medication (metformin or placebo) in 1274 patients in the original study who had not developed diabetes by the end of the trial. After the washout period, the authors report, the percentage of diabetes increased by 5.4% (from 25.2% to 30.6%) in the group of patients who had been assigned to metformin and by 3.3% (from 33.4% to 36.7%) in the placebo group.
Nine of 48 patients (19%) in the metformin group and 3 of 30 patients (10%) in the placebo group had not taken their coded medication for more than 90 days before their washout glucose tolerance test, the report indicates.
When both the study and the washout period were combined, the odds of diabetes were still reduced by 25% in the metformin group compared with the placebo group (p = 0.005), the researchers note, demonstrating “that a transient pharmacological effect did not explain the overall difference between metformin and placebo.”
” It appears that approximately one quarter of the beneficial effect of metformin to prevent type 2 diabetes in the DPP was attributable to a pharmacological effect that did not persist when the drug was withdrawn,” the authors conclude. “However, the overall effect of metformin in preventing diabetes remained a substantial 25% after withdrawal, concordant with the conclusion of the DPP that metformin reduces the conversion to diabetes in individuals with impaired glucose tolerance.”
” How long the effects of metformin on the underlying pathophysiology of diabetes might last is unknown, since the washout period rarely exceeded 14 days,” the investigators add. Diabetes Care 2003;26:977-980.
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FACT: The Diabetes Prevention Program found that diet and exercise resulting in a 5- to 7-percent weight loss lowered the incidence of type 2 diabetes by 58 percent. Participants lost weight by cutting fat and calories in their diet and by exercising (most chose walking) at least 30 minutes a day, 5 days a week.