The DPP-4 inhibitors are a class of agents that act as incretin enhancers. By inhibiting the DPP-4 enzyme, Sitagliptin increases the levels of two known active incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). The incretins are part of an endogenous system involved in the physiologic regulation of glucose homeostasis. When blood glucose concentrations are normal or elevated, GLP-1 and GIP increase insulin synthesis and release from pancreatic beta cells. GLP-1 also lowers glucagon secretion from pancreatic alpha cells, leading to reduced hepatic glucose production. This mechanism is unlike the mechanism seen with sulfonylureas; sulfonylureas cause insulin release even when glucose levels are low, which can lead to sulfonylurea-induced hypoglycemia in patients with type ll diabetes and in normal subjects. Sitagliptin demonstrates high selectivity for DPP-4 and does not inhibit closely-related enzymes DPP-8 or DPP-9 at therapeutic concentrations.
The recommended dose of Sitagliptin is 100 mg once daily as monotherapy or as combination therapy with Metformin, a sulfonylurea, a thiazolidinedione, or Metformin plus a sulfonylurea. Sitagliptin can be taken with or without food.
Elderly: No dosage adjustment is required based solely on age. The drug is excreted by the kidney. As elderly patients are more likely to have decreased renal function, caution should be taken in dose selection in the elderly.
Pediatric use: There is no data on use of Sitagliptin in patients younger than 18 years of age and therefore not recommended.