Multicenter retrospective assessment of thiazolidinedione monotherapy and combination therapy in patients with type 2 diabetes: comparative subgroup analyses of glycemic control and blood lipid levels

Background : Thiazolidinediones (TZDs) have contributed to the management of patients with type 2 diabetes mellitus as unique insulin-sensitizing agents. When used as monotherapy or in combination therapy, these drugs not only reduce glycosylated hemoglobin (HbA 1c ) levels, but also effect changes in blood lipid concentrations and have the potential to ameliorate cardiovascular disease risk. Although drugs in the TZD class are perceived to be equivalent clinically, prospective and retrospective studies have demonstrated their ability to modify blood lipid levels. Objective : We evaluated and compared the effects of pioglitazone and rosiglitazone monotherapy and combination therapy on blood lipid levels and HbA 1c in patients with type 2 diabetes. Methods : We conducted a multicenter retrospective chart review of 1115 records of patients with type 2 diabetes who received pioglitazone or rosiglitazone, alone or in combination with other antidiabetic agents, between August 1, 1999, and August 31, 2000. The review was conducted to evaluate pretreatment and posttreatment levels of triglyceride, total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and HbA 1c . Results : All observed demographic characteristics, comorbidities, and concomitant drug use were similar in both treatment cohorts. Of the patients who received pioglitazone, 83% also received >_1 other antihyperglycemic agent and 59% received some form of antihyperlipidemic therapy. Among those who received rosiglitazone, 81% received concomitant antihyperglycemic medication and 60% received some form of antihyperlipidemic therapy. With pioglitazone, mean levels of serum triglyceride, total cholesterol, and LDL-C decreased and HDL-C increased in most patients, with or without concomitant antihyperglycemic medications; with rosiglitazone, with or without other antidiabetic agents, triglyceride and HDL-C levels decreased, whereas total cholesterol and LDL-C levels increased in most patients. Reductions in HbA 1c levels and increases in body weight related to each study drug were comparable. Conclusions : This comparative assessment of pioglitazone and rosiglitazone, based on observational data, reveals that use of these TZDs with other antidiabetic agents was similar in 605 primary care practices in the United States. In both monotherapy and combination treatment regimens, pioglitazone was associated with greater beneficial effects on lipids than was rosiglitazone. Additional studies are needed to determine the long-term outcomes of TZD therapy with concomitant antihyperglycemic medications.