Treatment choice and effectiveness of adding sulphonylurea or glitazones to metformin for the treatment of type 2 diabetes mellitus

Aim: This study investigates the treatment choice between, and the effectiveness of, adding sulphonylurea or glitazone to ongoing metformin therapy for patients with type 2 diabetes mellitus in the clinical practice setting. Methods: A multicentre observational study using data from clinical records was conducted in Finland, France, Germany, Norway, Poland, Spain and the UK. Data were collected for patients who added sulphonylurea or glitazone to metformin. Effectiveness was defined as a change in haemoglobin A1c (HbA_1c) from baseline to approximately 1 year after the initiation of additional therapy. To allow for comparisons between the two medication regimens, propensity score matching was employed. Treatment choice was analysed using a probit regression model. We hypothesized that treatment choice was associated with factors reflecting patient’s characteristics, patient’s experience with diabetes, patient‘s health or to physician’s characteristics at baseline. Results: Compared with baseline, adding sulphonylurea to metformin reduced HbA_1c by 0.8% (p < 0.0001), while adding glitazone to metformin reduced HbA_1c by 0.9% (p < 0.0001). Percentage at HbA_1c goal (6.5%) increased from 6.9 to 23.8% for the sulphonylurea group and 8.3 to 33.3% for the glitazone group. Both groups had similar changes in high‐density lipoprotein cholesterol, low‐density lipoprotein cholesterol and triglycerides. In the probit regression model, age, HbA_1c, weight, treatment for weight reduction, history of macrovascular complications and type of physician were significant factors associated with treatment choice. Conclusions: This study is consistent with the results of long‐term randomized clinical trials in a clinical practice setting. Both regimens were able to reduce HbA_1c by about 1%.