Metformin in noninsulin-dependent diabetes mellitus.

Metformin is an oral antihyperglycemic agent that is approved by the Food and Drug Administration for the treatment of noninsulin-dependent diabetes mellitus. It differs from the sulfonylureas in that it is does not enhance insulin secretion and normally does not produce hypoglycemia. Metformin acts to decrease preprandial and postprandial blood glucose concentrations by increasing skeletal muscle uptake of glucose, decreasing gluconeogenesis, and decreasing absorption of glucose. The addition of metformin to maximum dosages of a sulfonylurea may synergistically improve glucose control. The drug may offer other potential benefits, such as weight loss or minimal weight gain, improved blood flow in patients with peripheral vascular disease, reduction of tissue plasminogen activator inhibitor, and improved lipid profiles. It is relatively safe if taken appropriately. Its most common side effects are gastrointestinal (nausea, diarrhea, anorexia), metallic taste, and vitamin B12 malabsorption. Lactic acidosis may also occur, but it is rare if metformin is avoided in patients with contraindications to its use. With careful monitoring, the agent may be considered for the initial treatment of obese patients who fail dietary measures, and those whose disease is refractory to maximum dosages of sulfonylureas or who do not tolerate them.