There are now eleven classes of medications for the treatment of type 2 diabetes.

Some have been available for many years, but some have recently been approved for use in diabetes.
They are listed in the order of approval by the FDA.

1. Insulin. Available since 1922. Drawbacks: must be given by injection; may cause hypoglycemia; frequently associated with weight gain. Advantage: Insulin always works to bring down blood sugar when given in sufficient dose.
2. Sulfonylureas, sometimes called "SU's". Many different SU's are available, and most are available as generic versions; see separate webpage. Sulfonylureas cause insulin release from the beta cells of the pancreas; they may cause severe hypoglycemia. The first sulfonylureas became available in the 1950's.
3. Biguanides: Metformin; see separate webpage. Initially available only as the brand-name version Glucophage, metformin is now available generically, and in varying forms, including a liquid and long-acting versions. Metformin was sold in Europe and many other countries for years before it was approved in the United States in 1995.

   An earlier drug in the biguanide class (phenformin) was withdrawn from sale in 1977 because of a high risk of a complication called lactic acidosis.

4. Alpha-glucosidase inhibitors. Acarbose (brand name Precose in the US, and Glucobay elsewhere): see separate webpage; first available in 1996. A second drug in the class is Miglitol (brand name Glyset). This class of drugs work in the intestine, by slowing down the digestion of carbohydrates, and lengthening the time it takes for carbohydrates to convert to glucose, thereby facilitating better blood glucose control, but mainly influence the level of blood sugar after eating. Drawbacks: Minimal glucose-lowering effects; need to be taken several times daily; frequently cause gastrointestinal side effects.
5. Thiazolidinediones, also called TZDs or "glitazones." The first agent in this class, troglitazone (brand name Rezulin) became available in 1997, but was withdrawn from the market when it became clear that it had a risk of toxic effects on the liver. Other approved TZDs are rosiglitazone (Avandia) and pioglitazone (Actos). These two medications do not have the risk of liver toxicity, but have other side effects (see individual pages for discussion). TZDs improve the action of insulin at the liver, muscles, and fat tissues (so they are sometimes called "insulin sensitizers").
6. Meglitinides. The first megltinide was replaglinide (brand name Prandin) in late 1997; the second was nateglinide (Starlix). These were short-acting drugs that work very similarly to the sulfonylureas, require dosing several times daily.
7. Amylin analogs. Pramlintide (brand name Symlin) is a synthetic analog of the human hormone amylin; see separate webpage. Pramlintide is an injectible medication, only for people who are already taking insulin, whether they have type 1 or type 2 diabetes. First available in 2005.
8. GLP-1 analogs (also called incretin mimetics). Exenatide (brand name Byetta) is an injectible medication for people with type 2 diabetes; see separate webpage; first available in 2005. Another GLP-1 analog, liraglutide (Victoza) is approved in Europe but not in the US; see separate webpage. Incretins, including the peptide GLP-1 (glucagon-like peptide-1), cause increased insulin secretion and other positive effects on diabetes. Side effects of exenatide include gastrointestinal effects, and weight loss.
9. DPP-4 inhibitors. The first dipeptidyl peptidase-4 (DPP-4) inhibitor to be approved was sitagliptin, brand name Januvia; see separate webpage. It became available in the US in 2006. Another DPP-4 inhibitor, vildagliptin (Galvus) is approved in Europe but not in the US; see separate webpage. DPP-4 is an enzyme that results in degradation of incretins such as GLP-1; DPP-4 inhibitors thus allow increased incretin levels. As incretins cause increased insulin secretion and other positive effects on diabetes, DPP-4 inhibitors indirectly cause improved glucose levels.
10. Bile acid sequestrants. Colesevelam (Welchol), originally approved (in 2000) for treatment of hyperlipidemia, was approved in 2008 for treatment of type 2 diabetes in combination with other diabetes drugs. The mechanism by which colesevelam improves glycemic control is unknown. See separate webpage.
11. Dopamine receptor agonists. Bromocryptine (brand name Cycloset) works in the brain "to reset hypothalamic centers regulating postprandial insulin-mediated glucose and lipid metabolism to thereby reduce postprandial hyperglycemia and hyperlipidemia." Side effects include Orthostatic hypotension (low blood pressure upon standing), nausea, fatigue, dizziness, vomiting, and headache. Previously approved for use in other conditions, it was approved for use in type 2 diabetes in 2009. See separate webpage.