Acarbose

Acarbose is an anti-diabetic drug used to treat type 2 diabetes mellitus and, in some countries, prediabetes. It is sold in Europe under the brand name Glucobay® (Bayer AG), in North America as Precose® (Bayer AG), and in Canada as Prandase® (Bayer AG). It is an inhibitor of alpha glucosidase, an enteric enzyme that releases glucose from larger carbohydrates.

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Mechanism of action

Acarbose inhibits enzymes (glycoside hydrolases) needed to digest carbohydrates: specifically alpha-glucosidase enzymes in the brush border of the small intestines and pancreatic alpha-amylase. Pancreatic alpha-amylase hydrolyzes complex starches to oligosaccharides in the lumen of the small intestine, whereas the membrane-bound intestinal alpha-glucosidases hydrolyze oligosaccharides, trisaccharides, and disaccharides to glucose and other monosaccharides in the small intestine. Inhibition of these enzyme systems reduces the rate of digestion of complex carbohydrates. Less glucose is absorbed because the carbohydrates are not broken down into glucose molecules. In diabetic patients, the short-term effect of these drugs therapies is to decrease current blood glucose levels: the long term effect is a small reduction in Hb_A1c level.^[1]

Dosing

Since acarbose prevents the digestion of complex carbohydrates, the drug should be taken at the start of main meals. (Taken with first bite of meal.) Moreover, the amount of complex carbohydrates in the meal will determine the effectiveness of acarbose in decreasing postprandial hyperglycemia. Adults are to take doses of 25mg 3 times daily.

Side effects

Since acarbose prevents the degradation of complex carbohydrates into glucose, the carbohydrates will remain in the intestine. In the colon, bacteria will digest the complex carbohydrates, thereby causing gastrointestinal side effects such as flatulence (78% of patients) and diarrhea (14% of patients).

Since these effects are dose-related, it is generally advised to start with a low dose and gradually increase the dose to the desired amount.

If a patient using acarbose suffers from a bout of hypoglycemia, the patient should eat something containing monosaccharides, such as glucose tablets. Since acarbose will prevent the digestion of complex carbohydrates, starchy foods will not effectively reverse a hypoglycemic episode in a patient taking acarbose.

References