Updated May 19, 2006

Alpha-Glucosidase Inhibitors

A class of diabetes drugs sometimes called “starch blockers” that blocks the action of enzymes that normally begin to break down certain carbohydrates in the upper part of the small intestine.

Different classes of diabetes medicines work in different ways to control high blood glucose. Biguanides such as metformin (brand name Glucophage) decrease the production of glucose in the liver. Sulfonylureas (Amaryl, DiaBeta, Glucotrol, Micronase) and meglitinides (Prandin, Starlix) stimulate the pancreas to release more insulin. Thiazolidinediones (Actos, Avandia) increase the sensitivity of fat and muscle cells to insulin.

Taken with the first bite of a meal, alpha-glucosidase inhibitors are especially well-suited to treat postprandial hyperglycemia (a sharp rise in blood sugar after meals), a common and serious problem faced by many people with Type 2 diabetes. Because the drugs prevent the immediate breakdown of starches into monosaccharides, or simple sugars, which would be absorbed into the bloodstream quickly, more of the carbohydrate consumed at a meal gets absorbed further “downstream” in the gastrointestinal tract, toward the end of the small intestine or the colon. Slowing the absorption of carbohydrate gives the beta cells in the pancreas more time to secrete adequate insulin to cover the meal.

Because of their novel mechanism of action, these drugs can also be combined effectively with other classes of diabetes drugs. However, while alpha-glucosidase inhibitors themselves do not cause low blood glucose, when they are used in combination with another diabetes medicines, hypoglycemia can occur. In addition, because these drugs slow the absorption of certain carbohydrates (including orange juice and white sugar), these sources will not work immediately to treat an episode of hypoglycemia. Pure glucose, in the form of gel or tablets, is the best treatment for hypoglycemia in this case.

One of the biggest drawbacks to the alpha-glucosidase inhibitors is their side effects. Because they affect carbohydrate absorption in the small intestine, they can cause bloating, nausea, diarrhea, and flatulence. Usually, these side effects can be minimized by starting therapy with a small dose and slowly working up to the most effective dose. These side effects also tend to diminish over time.

The first alpha-glucosidase inhibitor to become available in the United States was acarbose (Precose), which was approved by the U.S. Food and Drug Administration in 1995. A second alpha-glucosidase inhibitor, miglitol (Glyset) became available in 1999. They may be used by people with either Type 1 or Type 2 diabetes.

This article was written by Robert S. Dinsmoor, a Contributing Editor of Diabetes Self-Management.

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