with lab rats published in 2009 concluded that some of the possible risks of pancreatitis or pancreatic cancer may be reduced when it is used with metformin. However, while DPP-4 inhibitors showed an increase in such risk factors, as of 2009, no increase in pancreatic cancer has been reported in individuals taking DPP-4 inhibitors. In 2015, the U.S. Food and Drug Administration (FDA) added a new warning and precaution about the risk of "severe and disabling" joint pain to the labels of all DPP-4 inhibitor medicines. Mechanism of action Sitagliptin works to competitively inhibit the enzyme dipeptidyl peptidase 4 (DPP-4). This enzyme breaks down the incretins GLP-1 and GIP, gastrointestinal hormones released in response to a meal. By preventing breakdown of GLP-1 and GIP, they are able to increase the secretion of insulin and suppress the release of glucagon by the alpha cells of the pancreas. This drives blood glucose levels towards normal. As the blood glucose level approaches normal, the amounts of insulin released and glucagon suppressed diminishes, thus tending to prevent an "overshoot" and subsequent low blood sugar (hypoglycemia), which is seen with some other oral hypoglycemic agents. Sitagliptin has been shown to lower HbA1c level by about 0.7% points versus placebo. It is slightly less effective than metformin when used as a monotherapy. It does not cause weight gain and has less hypoglycemia compared to sulfonylureas. Sitagliptin is recommended as a second-line drug (in combination with other drugs) after the combination of diet/exercise and metformin fails. History Sitagliptin was approved by the U.S. Food and Drug Administration (FDA) in October 2006, and is marketed in the US as Januvia by Merck & Co. On April 2, 2007, the FDA approved an oral combination of sitagliptin/metformin sold in the US under the brand name Janumet. On October 7, 2011, the FDA approved an oral combination of sitagliptin/simvastatin marketed in the US as Juvisync. References External links Wikipedia medicine articles ready to translate Dipeptidyl peptidase-4 inhibitors Carboxamides Trifluoromethyl compounds Fluoroarenes Triazoles Merck & Co. brands