Common name in Nepal: Acarbose (Glucobay)
What Are Alpha-Glucosidase Inhibitors?
Alpha-glucosidase inhibitors are oral diabetes medications, of which acarbose is by far the most widely used. Unlike most diabetes drugs, they act almost entirely within the intestine rather than being absorbed into the bloodstream, and they specifically target the after-meal (postprandial) blood sugar spike rather than fasting blood sugar.
Mechanism of Action
Alpha-glucosidase inhibitors block enzymes on the lining of the small intestine that break down complex carbohydrates and disaccharides into simple, absorbable sugars. By slowing this digestion, they delay and blunt the rise in blood glucose that normally follows a carbohydrate-containing meal. Because the drug itself is barely absorbed and acts locally in the gut, its side effects are almost entirely digestive in nature. The undigested carbohydrate that reaches the colon is fermented by gut bacteria, which is the direct cause of the gas and bloating commonly seen with this class.
Benefits
Alpha-glucosidase inhibitors are particularly good at controlling the after-meal glucose spike and can lower HbA1c by roughly 0.5 to 0.8 percentage points. They do not cause weight gain and, used alone, do not cause hypoglycemia. They can be a useful add-on for patients whose main problem is high sugar readings after meals despite reasonable fasting levels.
Side Effects
Flatulence is extremely common — reported in a large majority of users — and is a direct, predictable consequence of undigested carbohydrate being fermented by bacteria in the colon.
Bloating, abdominal discomfort, and diarrhea are also frequent, particularly during the first weeks of treatment or after a dose increase; these tend to lessen over time as the gut adjusts, and can be minimized by starting at a low dose and increasing gradually.
Rare but more serious bowel effects, such as pneumatosis cystoides intestinalis (gas-filled cysts in the bowel wall), have been reported very rarely in long-term users.
Hypoglycemia when combined with other agents — if a patient is also on a sulfonylurea or insulin and develops hypoglycemia, it is important to know that regular table sugar (sucrose) will not correct it quickly, because acarbose blocks its breakdown; glucose tablets or gel (pure glucose, not sucrose) should be used instead.
Precautions
Because of its gut-related mechanism, alpha-glucosidase inhibitors should be avoided in people with significant inflammatory bowel disease, partial bowel obstruction, or other chronic intestinal disorders. The tablet must be taken with the first bite of each main meal to work properly — taking it between meals or on an empty stomach reduces its effectiveness and can worsen gastrointestinal side effects. Patients on concurrent sulfonylurea or insulin should be specifically counseled to treat any hypoglycemia with pure glucose rather than regular sugar or juice with high sucrose content.
Required Tests: Before and After Starting
There is no mandatory blood test required specifically before starting acarbose, though baseline liver function is sometimes checked, since rare cases of liver enzyme elevation have been reported. HbA1c is checked every 3 to 6 months as with other oral agents, and post-meal (postprandial) glucose readings are particularly useful for monitoring response, since this is the specific target of this drug class.
Sources
LiverTox. "Acarbose." NCBI Bookshelf, NBK548181.
Scientific overview, "Alpha Glucosidase Inhibitor," ScienceDirect Topics.
Hoffmann J, Spengler M. "Efficacy of 24-week monotherapy with acarbose, glibenclamide, or placebo in NIDDM patients." Diabetes Care.
Balfour JA, McTavish D. "Acarbose: an update of its pharmacology and therapeutic use in diabetes mellitus." Drugs, 1993.