Metformin added to insulin therapy for type 1 diabetes mellitus in adolescents

Diabetes mellitus is a metabolic disorder resulting from a defect in insulin secretion, insulin action, or both. Metabolic control (glycaemic control, that is long-term blood glucose levels as measured by glycosylated haemoglobin A1c (HbA1c)) often deteriorates during puberty in children with type 1 diabetes possibly due to the development of insulin resistance (insulin does not work effectively in the tissues anymore) and this creates a great need for alternative therapeutic strategies in those patients. We searched for randomised controlled trials of good quality that studied the effects of metformin added to insulin therapy for type 1 diabetes mellitus in adolescents on glycaemic control, insulin sensitivity, health-related quality of life, side-effects as well as effects on body weight, serum lipids and insulin dose.
Only two trials (60 participants, three months treatment) could be included. Both studies suggested that metformin plus insulin treatment lowered HbA1c somewhat more than placebo plus insulin. Improvement in insulin sensitivity, body weight or serum lipids were not seen in either study. However, one study showed a small decrease in insulin dosage by 10%. Side effects were mainly gastrointestinal upset in both studies and hypoglycaemia (low blood sugar) in one study. There was no information on health-related quality of life, costs, morbidity or mortality in either study.