Uses
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Diabetes Mellitus
Sitagliptin is used as monotherapy as an adjunct to diet and exercise to improve glycemic control in patients with type 2 diabetes mellitus. Sitagliptin is used as initial therapy in combination with metformin hydrochloride (given separately or as the fixed combination) as an adjunct to diet and exercise to improve glycemic control in patients with type 2 diabetes mellitus when treatment with both sitagliptin and metformin is appropriate. Sitagliptin also is used in combination with other oral antidiabetic agents (e.g., metformin, a sulfonylurea, a thiazolidinedione [peroxisome proliferator-activated receptorγ agonist]) or insulin as an adjunct to diet and exercise in patients with type 2 diabetes mellitus who have not achieved adequate glycemic control with one or more oral antidiabetic agents and/or insulin.
While metformin generally is the preferred antidiabetic agent for initial therapy in patients with type 2 diabetes mellitus, the American Association of Clinical Endocrinologists/American College of Endocrinology (AACE/ACE) suggests a dipeptidyl peptidase-4 (DPP-4) inhibitor as one of several alternative antidiabetic agents for initial monotherapy in patients with a contraindication to metformin (e.g., renal disease, hepatic disease, GI intolerance, risk of lactic acidosis). DPP-4 inhibitors also are recommended by AACE/ACE as part of combination therapy, particularly when both postprandial and fasting plasma glucose concentrations are elevated.
Sitagliptin should not be used in patients with type 1 diabetes mellitus or for the treatment of diabetic ketoacidosis.
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Sitagliptin Monotherapy
Efficacy of sitagliptin as monotherapy for the management of type 2 diabetes mellitus is supported by results of 2 controlled trials of 18 or 24 weeks' duration. Sitagliptin (100 or 200 mg once daily) improved glycemic control, as evidenced by reductions in glycosylated hemoglobin (hemoglobin A1c [HbA1c]) as well as fasting and 2-hour postprandial plasma glucose concentrations, compared with placebo. HbA1c was reduced by 0.5-0.6% (from an average baseline value of about 8%) in patients receiving sitagliptin 100 mg daily, compared with an increase of 0.1-0.2% in those receiving placebo. Overall, use of a higher than recommended dosage of sitagliptin (200 mg daily) did not provide greater glycemic control than did the recommended dosage of 100 mg daily.
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Combination Therapy
Efficacy of the combination of sitagliptin and metformin as initial therapy in patients with type 2 diabetes mellitus inadequately controlled with diet and exercise is supported by results of a 24-week randomized, placebo-controlled trial. In this trial, patients receiving initial therapy with sitagliptin (50 mg twice daily) in combination with metformin hydrochloride (500 mg or 1 g twice daily) had greater improvements in HbA1c, fasting plasma glucose, and 2-hour postprandial glucose concentrations than those receiving placebo, metformin monotherapy, or sitagliptin monotherapy. Mean reductions in HbA1c from baseline in patients not receiving an antihyperglycemic agent at trial entry were 1.1% with sitagliptin 100 mg once daily, 1.1% with metformin hydrochloride 500 mg twice daily, 1.2% with metformin hydrochloride 1 g twice daily, 1.6% with sitagliptin 50 mg twice daily in combination with metformin hydrochloride 500 mg twice daily, 1.9% with sitagliptin 50 mg twice daily in combination with metformin hydrochloride 1 g twice daily, and 0.2% with placebo. In the same study, patients with more severe hyperglycemia (HbA1c exceeding 11% or blood glucose exceeding 280 mg/dL) who received sitagliptin (50 mg twice daily) in combination with metformin hydrochloride (1 g twice daily) on an open-label basis achieved mean reductions from baseline of 2.9% in HbA1c, 127 mg/dL in fasting plasma glucose, and 208 mg/dL in 2-hour postprandial glucose by the end of the trial (at 24 weeks).
In another 24-week, randomized trial in patients who had inadequate glycemic control with diet and exercise, initial therapy with the combination of sitagliptin (100 mg once daily) and pioglitazone (30 mg once daily) produced greater improvements in HbA1c, fasting plasma glucose, and 2-hour postprandial glucose concentrations than pioglitazone monotherapy (30 mg once daily). In this trial, patients receiving the sitagliptin/pioglitazone combination achieved a 0.9% mean reduction in HbA1c compared with those receiving pioglitazone monotherapy, and 60% of patients receiving sitagliptin/pioglitazone achieved a mean HbA1c less than 7%, compared with 28% of those receiving pioglitazone monotherapy.
Efficacy of sitagliptin in combination with metformin, a sulfonylurea, and/or a thiazolidinedione in the management of type 2 diabetes mellitus (in patients inadequately controlled with metformin or thiazolidinedione monotherapy) is supported by results from several long-term (24 weeks' duration), randomized, placebo-controlled trials. In these trials, the addition of sitagliptin (100 mg once daily) to existing metformin and/or glimepiride therapy or to pioglitazone or rosiglitazone/metformin therapy improved glycemic control, as evidenced by reductions in HbA1c as well as fasting and/or 2-hour postprandial plasma glucose concentrations, compared with placebo or existing therapy. In patients receiving metformin hydrochloride therapy (dosage of at least 1.5 g daily), the addition of sitagliptin resulted in a reduction of 0.7% in HbA1c, while the addition of placebo resulted in no appreciable change in HbA1c. In patients receiving glimepiride therapy (dosage of at least 4 mg daily), the addition of sitagliptin resulted in a reduction of 0.6% in HbA1c compared with addition of placebo. In patients receiving glimepiride (dosage of at least 4 mg daily) in combination with metformin hydrochloride (dosage of at least 1.5 g daily), the addition of sitagliptin resulted in a reduction of 0.9% in HbA1c compared with addition of placebo. In patients receiving pioglitazone therapy (30-45 mg daily), the addition of sitagliptin or placebo resulted in reductions of 0.9 or 0.2%, respectively, in HbA1c. In patients receiving metformin and rosiglitazone therapy in a 54-week trial, addition of sitagliptin 100 mg once daily or placebo resulted in mean reductions in HbA1c of 1 or 0.3%, respectively; sulfonylurea (e.g., glipizide) rescue therapy was used in 18 or 40% of patients receiving sitagliptin or placebo, respectively. In a 52-week noninferiority trial in patients receiving metformin hydrochloride (dosage of at least 1.5 g daily), add-on therapy with sitagliptin (100 mg once daily) or glipizide (5-20 mg once daily; mean 10 mg once daily) was associated with similar mean reductions from baseline in HbA1c (intent-to-treat analysis); results may be applicable principally to patients with baseline HbA1c values less than 8-9%, comparable to those of this study population.
Efficacy of sitagliptin in combination with insulin (with or without metformin) in the management of type 2 diabetes mellitus in patients who have inadequate glycemic control with insulin is supported by results of a 24-week, randomized, placebo-controlled trial. In this trial, addition of sitagliptin (100 mg once daily) to existing stable insulin (premixed insulin or intermediate- or long-acting insulin) therapy with or without metformin hydrochloride (dosage of at least 1.5 g daily) resulted in improvements in HbA1c, fasting plasma glucose, and 2-hour postprandial glucose concentrations compared with addition of placebo. In patients who received sitagliptin as add-on therapy to metformin and insulin, 14% had HbA1c reductions to less than 7% compared with 5% of those receiving add-on placebo with metformin and insulin. Among patients also receiving metformin, the median daily dosage of insulin at baseline for patients treated with sitagliptin or placebo was 40 or 42 units, respectively; the median daily insulin dosage for both groups at the end of the study was unchanged. Patients in both treatment groups gained a mean of 0.1 kg of body weight over the study period; hypoglycemia was more common in patients receiving add-on sitagliptin therapy.
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