[One year persistence of metformin monotherapy versus metformin/sitagliptin fixed dose combination]

Introduction: In treatment of type 2 diabetes mellitus it is important to reach glycaemic targets. The elements of this are the adequate diet and the patient's adherence to medication.

Aim: The aim of the authors was to investigate the one year persistence of the metformin monotherapy and sitagliptin/metformin fixed dose combination in type 2 diabetic patients.

Method: National Health Insurance Found prescriptions database of Hungary on pharmacy-claims between October 1, 2012 and September 30, 2013 was analyzed. The authors identified patients who filled prescriptions for metformin monotherapy and fixed dose combinations of sitagliptin/metformin prescribed for the first time. Patients have not received similar drugs one year previous to study. To model the persistence, the apparatus of survival analysis was used, where "survival" was the time to abandon the medication. As it was available to month precision, discrete time survival analysis was applied: a generalized linear model was estimated with complementary log-log link function with the kind of drug being the only explanatory variable.

Results: During the trial period, metformin monotherapy or sitagliptin/metformin fixed dose combination was started in 63,386 and 10,039 patients, respectively. One year persistence rate in patients with metformin monotherapy was 30%, and 58% in patients with sitagliptin/metformin fixed dose combination. Considering only the 360-day study period, the mean duration of persistence was 173.4 days in patients on metformin monotherapy and 261.9 days on sitagliptin/metformin fixed dose combination. The hazard of discontinuation was more than twofold higher during treatment with metformin monotherapy compared with the use of the sitagliptin/metformin fixed dose combination (hazard ratio = 2.267, p<0.001).

Conclusions: There is a significant difference between the one year persistence of metformin monotherapy and sitagliptin/metformin fixed dose combination in type 2 diabetic patients. The result demonstrated sitagliptin/metformin fixed dose combination has a favourable patients' adherence as compared to metformin monotherapy.