Oral antidiabetic agents. The emergence of alpha-glucosidase inhibitors.

Hyperglycaemia in patients with non-insulin-dependent diabetes mellitus (NIDDM) results from impaired insulin action and/or deficient insulin secretion. These abnormalities lead to increased hepatic glucose production, the primary cause of fasting hyperglycaemia, and decreased peripheral glucose uptake, the major mechanism responsible for postprandial hyperglycaemia. Hyperglycaemia in patients with NIDDM can be decreased by several different mechanisms: (1) a decrease in nutrient ingestion; (2) an increase in insulin secretion; (3) a decrease in hepatic glucose production; (4) an increase in peripheral glucose uptake. Oral agents used to treat NIDDM operate through 1 or more of the above mechanisms. alpha-Glucosidase inhibitors, a new class of drugs that delay carbohydrate digestion and absorption, reduce postprandial glycaemic rises by about 3 mmol/L. Metformin decreases fasting and postprandial hyperglycaemia through increasing glucose uptake and perhaps decreasing appetite. Sulphonylureas lower hyperglycaemia by increasing insulin secretion and to a lesser degree potentiating insulin action on the liver and peripheral tissues. alpha-Glucosidase inhibitors are particularly useful as primary therapy for patients with mild to moderate hyperglycaemia and in those patients who may be at risk for hypoglycaemia or lactic acidosis. Sulphonylureas are indicated for the more severely hyperglycaemic NIDDM patients who are not yet candidates for insulin therapy. Metformin is useful in obese moderately hyperglycaemic NIDDM patients. These oral agents can be used in combination to give better glycaemic control than is possible with each alone.