Sitagliptin; sitagliptin and metformin; sitagliptin and metformin XR; sitagliptin 100 mg tablet, 28; sitagliptin 50 mg tablet, 28; sitagliptin 25 mg tablet, 28; sitagliptin 50 mg + metformin hydrochloride 1000 mg tablet, 56; sitagliptin 50 mg + metformin hydrochloride 850 mg tablet, 56; sitagliptin 50 mg + metformin hydrochloride 500 mg tablet, 56; sitagliptin 100 mg + metformin hydrochloride 1000 mg tablet: modified release, 28; sitagliptin 50 mg + metformin hydrochloride 1000 mg tablet: modified release, 56; Januvia®; Janumet®; Janumet XR®