Adherence, persistence, and treatment discontinuation with sitagliptin compared with sulfonylureas as add-ons to metformin: A retrospective cohort database study.

BackgroundData are limited regarding adherence to dipeptidyl peptidase-4 inhibitors. MethodsThe present retrospective cohort study of a claims database involved adults with type 2 diabetes mellitus, continuous enrollment for 12months before the first prescription of add-on sitagliptin (SITA) or a sulfonylurea (SU) to metformin (MET) monotherapy (index date), and 45days of MET coverage 90days before the index date. The SITA and SU users were matched on duration of follow-up and propensity score (PS). Logistic regression analysis incorporated age, gender, comorbidities, and concomitant medications as independent variables. ResultsApproximately 99% of SITA patients were PS matched, resulting in 14807 well-balanced PS-matched SITA/SU pairs. Mean proportion of days covered (PDC) was significantly higher for SITA (vs SU)+MET after 1year (P<0.001). Adherence (PDC 80%) to SITA (vs SU)+MET was 59.1% (vs 55.9%; P<0.001) at 1year and 52.6% (vs 49.9%; P=0.007) at 2years. Using logistic regression models including out-of-pocket expense (OPE) as a covariate, we found improved mean PDC and adherence for SITA (vs SU)+MET. Numbers of patients who continued to use SITA (vs SU)+MET were significantly higher after Years 1, 2, and 3 (all P<0.05). ConclusionsUsers of SITA + MET had significantly higher mean PDC, adherence, and persistence than those on SU+MET. These trends were robust to model alterations and were more marked when accommodating OPEs.