Which medication listed is a DPP-4 inhibitor used to treat type 2 diabetes mellitus?

• A. Metformin
• B. Januvia
• C. Invokana
• D. Byetta

Answer: (B)

DPP-4 inhibitors increase the level and activity of incretin hormones (GLP-1 and GIP) by blocking the enzyme that degrades them. This leads to enhanced glucose-dependent insulin secretion and reduced glucagon release after meals, helping lower blood glucose in type 2 diabetes. Januvia (sitagliptin) is a DPP-4 inhibitor, so it fits this mechanism.

Metformin works primarily by reducing hepatic glucose production and improving insulin sensitivity, not by affecting incretin breakdown. Invokana is an SGLT2 inhibitor, which promotes glucose excretion in the urine. Byetta is a GLP-1 receptor agonist, which directly stimulates the incretin receptor rather than inhibiting DPP-4.