Add-on metformin therapy did not improve glycemic control in overweight adolescents with type 1 diabetes, according to a report published online Dec. 1 in JAMA.
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Even though patients with type 1 diabetes are traditionally thought of as being underweight or of normal weight, the percentage who are overweight or obese is increasing in this patient population as it is in the general population. Being overweight or obese has serious metabolic consequences for patients with diabetes, particularly during adolescence, said Dr. Ingrid M. Libman, a pediatric endocrinologist at the Children’s Hospital of Pittsburgh, and her associates.
They assessed the effect of adding oral metformin (2,000 mg/day) to insulin therapy in a double-blind placebo-controlled trial involving 140 patients aged 12-19 years (mean age, 15.3 years) at 26 U.S. clinics. The study participants were overweight or obese and had had type 1 diabetes for a mean of 7 years.
The primary efficacy outcome – change in HbA1c level after 6 months of adjunctive metformin (71 patients) or matching placebo (69 patients) – was exactly the same, with an increase of 0.2% in both study groups. Continuous glucose monitoring confirmed that there were no significant differences between the two study groups in glycemic control.
Compared with patients taking placebo, those taking metformin showed a slight reduction in total daily insulin dose and a slightly lower weight gain. “The clinical relevance of these treatment group differences is uncertain,” Dr. Libman and her associates wrote (JAMA 2015 Dec 1. doi: 10.1001/jama.2015.16174). There were no differences between the two groups in blood pressure, lipid profiles, or inflammatory markers.
Patients taking metformin reported significantly more adverse gastrointestinal events than those taking placebo. And severe hypoglycemia developed in five patients taking metformin, compared with none who were taking placebo.
“These results do not support prescribing metformin to adolescents to improve glycemic control,” the investigators wrote.