Achieving glycemic control differs between patients with type 2 diabetes mellitus starting on metformin and sulfonylureas

Background: Antidiabetic medication is aimed at attaining tight glycemic control, but patients do not always achieve guideline recommended targets. Available observational studies focusing on both drug treatment and glycemic control have some methodological limitations. Objectives: To describe the relation between long-term medication use and changes in HbA1c level in various subgroups of patients with type 2 diabetes mellitus. Methods: A cohort study was performed among new users of metformin (Met) or sulfonylurea (SU), aged ≥ 35 years, enrolled in the Diabetes Care System (DCS) in the Dutch region of West-Friesland (200,000 inhabitants). Patients receiving care from the DCS were linked to drug dispensing data obtained from 15 community pharmacies and two dispensing general practices in the region. Patients visit the DCS annually for a check-up. The study period was between 1998 and 2007. To be eligible, subjects had to remain on the initially prescribed OAD for at least 3 years, have a Hba1c-measurement in 3 months around treatment start and have at least three Hba1c measurements overall. We categorised patients according to Hb1ac level at treatment initiation (≤ 7%, > 7%) and assessed time to reaching either a HbA1c > 7% or ≤ 7%, respectively. Cox regression analysis was conducted to compare Met and SU, while adjusting for confounders. Results: There were 382 and 149 starters of Met and SU, respectively. The majority of patients (63%) entered the cohort with a Hba1c > 7%. Patients initiating Met at an HbA1c > 7% showed a statistically significant faster progression to a HbA1c ≤ 7% compared to those starting SU (adjusted hazard ratio 0.74, 95%CI: 0.56-0.96). Stratification revealed no statistically significant differences between age, sex, and BMI subgroups. The proportion of patients with add-ons was high (50.5%). No difference between Met en SU was found among patients on monotherapy. In patients starting with an HbA1c ≤ 7% no obvious differences were observed between Met and SU. Conclusions: Overall results confirmed Met as the first choice OAD in T2DM patients with an HbA1c ≥ 7.0%, but treatment intensification in order to reach glycemic control is frequent.