Diabetes Oral Antidiabetic Drugs: Alpha-glucosidase Inhibitors

Acarbose (Glucobay) is the only drug in this group licensed for use in the UK but others are likely to become available in the future. Acarbose works in the small intestine by inhibiting alpha-glucosidases, which are enzymes that break down carbohydrates into glucose. Hence there is less glucose available to be absorbed into the blood and peaking of blood sugar levels is reduced. Acarbose is designed to be used immediately before or at the start of a carbohydrate-containing meal. The drug is metabolized by bacteria within the gut into inactive products which are eliminated in faeces or absorbed into the blood and eventually excreted by the kidneys in urine. Acarbose may be used as monotherapy before any other drugs are tried or it may be combined with other antidiabetic agents. Used alone, it does not cause hypoglycaemia but it may add to the hypoglycaemic potential of sulphonylureas or insulin, if used in combination.

Gastrointestinal upset is a common side-effect with acarbose and its manifestations include wind, diarrhoea and bloating. These symptoms occur because more carbohydrate passes unchanged into the large bowel where it is subjected to fermentation by gut bacteria. Symptoms are experienced by about one-third of those taking acarbose, especially by people being treated with higher dose regimes. However, symptoms tend to subside with time as the person adjusts to the drug. Strict avoidance of sugar in the diet and very minimal dose increases, introduced gradually, help to minimize unpleasant gastrointestinal symptoms. However, if symptoms persist, it may be necessary to try alternative medication. Acarbose does not cause weight gain and so is highly suitable for people with Type 2 diabetes, who are likely to be overweight. However, it can cause a rise in the plasma blood levels of certain liver enzymes and so it is not suitable for people with any impairment of liver function. Due to its gastrointestinal effects, it is also ruled out for people with various bowel disorders, including ulcerative colitis, inflammatory bowel disease, and obstructions of the bowel, such as hernias, irritable bowel syndrome and so on. It is not prescribed for people with severe kidney disorders or impairment of renal function.

The tablets are supplied in 50 mg and 100 mg dose sizes. The starting dose is 1 X 50 mg tablet taken with the first mouthful of the main daily meal. After two weeks, if the drug is well tolerated, the dose is increased to introduce a second 50 mg tablet with a different meal. This is followed for a further two weeks and then a third 50 mg tablet is introduced, taken with the remaining meal. If there are adverse side-effects, the dosage is dropped back to the previous level. After six weeks, the dose may be further increased in a gradual way, possibly introducing the 100 mg tablet with one meal. The maximum permitted dose is 3 X 100 mg tablets, each taken separately with one main meal. Acarbose may interact with the following drugs:

• pancreatic enzymes: used for disorders of the pancreas when there is a lack of digestive enzymes
• cholestyramine (Questran): used for relief of diarrhoea in biliary disorders and to treat hyperlipidaemia (raised blood fat levels)
• neomycin: an antibiotic used to treat infections within the intestine.

Get more information about other diabetes oral antidiabetic drugs