Effects of concomitant drugs on sitagliptin-mediated improvement in glycemic control in Japanese patients with type 2 diabetes.

Aims: We investigated to clarify factors associated with the efficacy of sitagliptin, a dipeptidyl peptidase (DPP)-IV inhibitor, for glycemic control including the confounding effect of concomitant drugs in patients with type 2 diabetes.

Methods: We included type 2 diabetes patients with HbA1c levels of ≥7% who were not under insulin treatment and were administered sitagliptin (50mg/day for 6 months). Reduction or discontinuation of insulin sensitizers was not permitted during the study period. Outcomes included HbA1c level variations and attaining a target HbA1c level of <7%. Associated factors with each outcome were examined using multivariate analysis.

Results: Of the 313 patients enrolled in this study, 147 (47.0%) attained HbA1c levels of <7%. High baseline HbA1c levels were associated with HbA1c level variations but inversely associated with attaining the target HbA1c level of <7%. Concomitant use of an insulin sensitizer and a α-glucosidase inhibitor and maintenance of the baseline dose of concomitant drugs were significantly associated with each outcome.

Conclusions: Our results suggest that concomitant sitagliptin administration (50mg/day) will improve glycemic control if treatment is initiated before HbA1c levels deteriorate. Other medication should be continued at initiation of sitagliptin administration.