Dipeptidyl peptidase -4 inhibitors represent a novel way to augment the incretin 
system and one of the newest class of medications in the treatment of type 2 
diabetes mellitus. Their mechanism of action is to decrease the inactivation of 
glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide, both 
of which are involved in maintaining euglycemia subsequent to carbohydrate 
intake. Currently investigated agents include sitagliptin, vildagliptin, 
saxagliptin, linagliptin, and alogliptin. Each agent has been shown to provide 
significant improvements in glycemic control compared to placebo. They are 
effective when added to other oral diabetes agents and in the cases of 
sitagliptin, vildagliptin, and alogliptin in addition to insulin. These agents 
may not provide as significant improvement in glucose concentrations as some 
other medications including metformin, thiazolidinediones, or glucagon-like 
peptide 1 agonists. The lack of head to head clinical data comparing the various 
dipeptidyl peptidase 4 inhibitors does not allow for specific recommendations if 
one agent is more effective or safer than another within the class. Their side 
effect profile suggests they are very well tolerated and have few drug 
interactions. For patients with mildly elevated glucose concentrations, they are 
therapeutic options in both drug-naive patients as well as those not optimally 
controlled on other diabetes medications.