Acarbose
Encyclopedia
Acarbose is an anti-diabetic drug
used to treat type 2 diabetes mellitus
and, in some countries, prediabetes
. It is a generic sold in Europe and China as Glucobay (Bayer AG
), in North America as Precose (Bayer Pharmaceuticals
), and in Canada as Prandase (Bayer AG
). It is cheap and popular in China, but not in the U.S., because it's not potent enough to justify the side effects of diarrhea and flatulation. It is a starch blocker, and inhibits alpha glucosidase, an intestinal enzyme that releases glucose
from larger carbohydrate
s. It is composed of an acarviosin
moiety with a maltose at the reducing terminus.
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 oligosaccharide
s, trisaccharides, and disaccharide
s to glucose
and other monosaccharide
s 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 reduction in HbA1c
level. This reduction averages an absolute decrease of 0.7%, which is a decrease of about 10% in typical HbA1c values in diabetes studies.
hyperglycemia
. Adults may take doses of 25 mg 3 times daily, increasing to 100 mg 3 times a day.
, bacteria digest the complex carbohydrates, causing gastrointestinal side-effects such as flatulence
(78% of patients) and diarrhea
(14% of patients). Since these effects are dose-related, in general it is advised to start with a low dose and gradually increase the dose to the desired amount. One study found that G.I. side effects decreased significantly (from 50% to 15%) over 24 weeks, even on constant dosing.
If a patient using acarbose suffers from a bout of hypoglycemia
, the patient must eat something containing monosaccharide
s, such as fruit juice or 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.
Hepatitis
has been reported with acarbose use. It usually goes away when the medicine is stopped. Therefore, liver enzymes should be checked before and during use of this medicine.
Anti-diabetic drug
Anti-diabetic medications treat diabetes mellitus by lowering glucose levels in the blood. With the exceptions of insulin, exenatide, and pramlintide, all are administered orally and are thus also called oral hypoglycemic agents or oral antihyperglycemic agents...
used to treat type 2 diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
and, in some countries, prediabetes
Prediabetes
Prediabetes is the state in which some but not all of the diagnostic criteria for diabetes are met. It is often described as the “gray area” between normal blood sugar and diabetic levels. While in this range, patients are at risk for not only developing type 2 diabetes, but also for cardiovascular...
. It is a generic sold in Europe and China as Glucobay (Bayer AG
Bayer
Bayer AG is a chemical and pharmaceutical company founded in Barmen , Germany in 1863. It is headquartered in Leverkusen, North Rhine-Westphalia, Germany and well known for its original brand of aspirin.-History:...
), in North America as Precose (Bayer Pharmaceuticals
Bayer
Bayer AG is a chemical and pharmaceutical company founded in Barmen , Germany in 1863. It is headquartered in Leverkusen, North Rhine-Westphalia, Germany and well known for its original brand of aspirin.-History:...
), and in Canada as Prandase (Bayer AG
Bayer
Bayer AG is a chemical and pharmaceutical company founded in Barmen , Germany in 1863. It is headquartered in Leverkusen, North Rhine-Westphalia, Germany and well known for its original brand of aspirin.-History:...
). It is cheap and popular in China, but not in the U.S., because it's not potent enough to justify the side effects of diarrhea and flatulation. It is a starch blocker, and inhibits alpha glucosidase, an intestinal enzyme that releases glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
from larger carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s. It is composed of an acarviosin
Acarviosin
Acarviosin is a sugar composed of cyclohexitol linked to a 4-amino-4,6-dideoxy-D-glucopyranose. Acarviosin is part of the potent α-amylase inhibitor acarbose and its derivatives. The nitrogen atom binds to α-amylase more tightly than the natural substrate making it more potent than other inhibitors...
moiety with a maltose at the reducing terminus.
Mechanism of action
Acarbose inhibits enzymes (glycoside hydrolases) needed to digest carbohydrates, to be specific, alpha-glucosidaseAlpha-glucosidase
Alpha-glucosidase is a glucosidase acting upon 1,4-alpha bonds. This is in contrast to beta-glucosidase.The term maltase, which refers to an enzyme cleaving maltose, is nearly equivalent.Types include:* Acid alpha-glucosidase* neutral** GANAB** GANC...
enzymes in the brush border of the small intestines and pancreatic alpha-amylase. Pancreatic alpha-amylase
Alpha-Amylase
α-Amylase is an enzyme that hydrolyses alpha-bonds of large alpha-linked polysaccharides such as starch and glycogen, yielding glucose and maltose. It is the major form of amylase found in humans and other mammals...
hydrolyzes complex starches to oligosaccharides in the lumen of the small intestine, whereas the membrane-bound intestinal alpha-glucosidases hydrolyze oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...
s, trisaccharides, and disaccharide
Disaccharide
A disaccharide or biose is the carbohydrate formed when two monosaccharides undergo a condensation reaction which involves the elimination of a small molecule, such as water, from the functional groups only. Like monosaccharides, disaccharides form an aqueous solution when dissolved in water...
s to glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
and other monosaccharide
Monosaccharide
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...
s 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 reduction in HbA1c
Glycosylated hemoglobin
Glycated hemoglobin is a form of hemoglobin that is measured primarily to identify the average plasma glucose concentration over prolonged periods of time. It is formed in a non-enzymatic glycation pathway by hemoglobin's exposure to plasma glucose...
level. This reduction averages an absolute decrease of 0.7%, which is a decrease of about 10% in typical HbA1c values in diabetes studies.
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 postprandialPostprandial
Postprandial means after eating a meal while preprandial is before a meal.-Usages of the term:This term is used in many contexts but also in relation to blood sugar levels, which are normally measured 2 hours after and before eating in a postprandial glucose test...
hyperglycemia
Hyperglycemia
Hyperglycemia or Hyperglycæmia, or high blood sugar, is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a glucose level higher than 13.5mmol/l , but symptoms may not start to become noticeable until even higher values such as 15-20 mmol/l...
. Adults may take doses of 25 mg 3 times daily, increasing to 100 mg 3 times a day.
Side-effects
Since acarbose prevents the degradation of complex carbohydrates into glucose, some carbohydrate will remain in the intestine and be delivered to the colon. In the colonColon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
, bacteria digest the complex carbohydrates, causing gastrointestinal side-effects such as flatulence
Flatulence
Flatulence is the expulsion through the rectum of a mixture of gases that are byproducts of the digestion process of mammals and other animals. The medical term for the mixture of gases is flatus, informally known as a fart, or simply gas...
(78% of patients) and diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
(14% of patients). Since these effects are dose-related, in general it is advised to start with a low dose and gradually increase the dose to the desired amount. One study found that G.I. side effects decreased significantly (from 50% to 15%) over 24 weeks, even on constant dosing.
If a patient using acarbose suffers from a bout of hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
, the patient must eat something containing monosaccharide
Monosaccharide
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...
s, such as fruit juice or 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.
Hepatitis
Hepatitis
Hepatitis is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. The name is from the Greek hepar , the root being hepat- , meaning liver, and suffix -itis, meaning "inflammation"...
has been reported with acarbose use. It usually goes away when the medicine is stopped. Therefore, liver enzymes should be checked before and during use of this medicine.
External links
- Precose (acarbose) Tablet - NIH Information [Bayer Pharmaceuticals Corporation]
- "Probing the Pancreas" - by Craig D. Reid, Ph.D. (US FDA Consumer Article)