Diabetes mellitus is a condition causing increased blood glucose levels; symptoms may include increased urination, increased thirst and extreme fatigue. If left untreated or poorly managed, high blood glucose levels may eventually result in kidney failure, amputation, blindness and death. Depending upon the body's ability to produce insulin, treatment can be chosen from a number of classes of diabetes medications.
Insulin
Several different forms of insulin are available in injectable or inhalation form to replace insulin that is normally manufactured by the body. Insulin replacement therapy is used for Type 1 diabetics who cannot manufacture insulin and by some Type 2 diabetics who do not manufacture enough insulin.
Sulfonylureas
Chlorpropamide, glimepiride, glyburide and glipizide are all members of the class of antidiabetic medications known as sulfonylureas. They work by stimulating insulin secretion from the pancreas, particularly after meals, and are used only for Type 2 diabetics. These medications may not be safe in those with severe kidney or liver impairment. In some patients, resistance to sulfonylureas develops, requiring the use of additional or alternative medications.
AG Inhibitors
Alpha-glucosidase (AG) inhibitors such as acarbose and miglitol work by delaying the digestion of carbohydrates. This effect results in a smaller rise in blood glucose levels following a meal. These drugs do not increase insulin secretion but can be used in combination with other antidiabetic medications such as sulfonylureas. Patients with intestinal or digestive disorders such as obstruction or inflammatory bowel disease should not take AG inhibitors. They are excreted by the kidney, and patients with compromised kidney function may require dosage adjustment.
Biguanides
The biguanide medication metformin is available as a single agent or in combination with other diabetes medications such as rosiglitazone, glyburide and glipizide. Metformin works by reducing release of glucose from storage in the liver, decreasing absorption of glucose in the digestive system and improving insulin sensitivity to increase glucose movement into cells. It may reduce the need for additional insulin doses. Metformin should not be used in those with renal disease or dysfunction and must be temporarily discontinued in patients undergoing certain radiologic procedures.
Glitazones
Members of the glitazone or thiazolidinedione class of antidiabetic drugs, including pioglitazone and rosaglitazone, depend on the presence of insulin for activity. Thus they are useful only for Type 2 diabetics. Glitazones work to decrease insulin resistance, increase glucose storage in the liver and decrease glucose release from the liver. Patients with congestive heart failure or liver disease may require dosage adjustment, and glitazones should not be used in those who have been diagnosed with advanced heart failure or active liver disease.
Meglitinides
The meglitinides include nateglinide and repaglinide, which work to lower blood glucose level by increasing insulin release from the pancreas in patients who can produce insulin. The amount of insulin release depends upon blood glucose levels and decreases with lower blood glucose levels. These medications are not useful for those with Type 1 diabetes and should not be given with the cholesterol-lowering medication gemfibrozil.
Incretins
Exenatide and pramlintide act similarly to gastrointestinal hormones known as incretins. They work to increase insulin release from the pancreas as well as suppressing suppressing glucagon release. They also slow gastric emptying time, which reduces the rate at which glucose can be absorbed from the small intestine. Incretins decrease both fasting and post-meal glucose concentration. Exitinide has been associated with acute pancreatitis and should not be used in patients with a history of pancreatitis or in those with significant renal impairment.
