Medium-Term Effect of Add-On Therapy with the DPP-4 Inhibitor, Sitagliptin, in Insulin-Treated Japanese Patients with Type 2 Diabetes Mellitus

INTRODUCTION A 12-week prospective study was previously performed to assess the effect of add-on therapy with sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, in patients with type 2 diabetes mellitus (T2DM) receiving insulin treatment. Patients were followed until week 48 to investigate the medium-term efficacy and safety of the add-on therapy with sitagliptin. METHODS In the 70 patients with T2DM, glycemic control, insulin dosage, concomitant medications, body weight, laboratory parameters, and adverse events were evaluated for 48 weeks. RESULTS Hemoglobin A1c (HbA1c) improved significantly from 8.03% at week 0 (at initiation of the add-on therapy) to 7.45% at week 48 (P < 0.01). Body weight remained nearly the same. The daily insulin dose was significantly reduced by 2.5 U, from 25.8 to 23.3 U/day (P < 0.001). Stratified analysis of the improvement of HbA1c based on age, duration of diabetes, body mass index, insulin regimen, and oral antidiabetic drugs did not identify any significant differences in relation to these parameters. During the 48-week follow-up period, there were no problematic adverse events, such as severe hypoglycemia, and the add-on therapy with sitagliptin showed good tolerability. CONCLUSIONS In Japanese patients with T2DM receiving insulin treatment, add-on therapy with sitagliptin was not associated with weight gain and allowed for the reduction of the insulin dosage. Consistent efficacy was noted for 48 weeks without an increasing hypoglycemic effect, and the add-on therapy with sitagliptin was effective irrespective of the insulin regimen.