Pioglitazone greatly decreases the risk of developing type 2 diabetes, especially for those who already have prediabetes and/or who have had strokes, according to a study also presented at the ADA.

The Insulin Resistance Intervention after Stroke trial (IRIS) recently found that the thiazolidinedione (TZD) drug, pioglitazone, reduced the risk of fatal and non-fatal stroke and myocardial infarction by 24% in people with cerebrovascular disease. This secondary analysis of the data collected in the IRIS trial examined pioglitazone's effect on diabetes prevention in a large group of non-diabetic stroke patients with insulin resistance, including many people who had prediabetes. The analysis found that pioglitazone reduced progression to diabetes by 52%.

The IRIS trial included 3,876 patients who recently had a stroke or heart attack, insulin resistance (defined as Homeostasis Model Assessment of Insulin Resistance >3.0) and who did not have diabetes (defined as no prior history and fasting plasma glucose of <126mg/ dl). They were randomly assigned to pioglitazone (45mg QD) (n=1,939) or placebo (n=1,937). At baseline, patients exhibited mean fasting plasma glucose levels (FPG) of 98.2mg/dl, A1C of 5.8 % and Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) of 5.4. They were assessed annually through interviews and FPG testing. After the first year, mean HOMA-IR dropped to 4.1 in the pioglitazone group and increased to 5.7 in the placebo group (p<0.0001), while FPG decreased to 95.1mg/dl in the pioglitazone group and increased to 99.7mg/dl in the placebo group (p<0.0001). During 4.8 years of follow up, 73 (3.8%) patients in the pioglitazone group developed type 2 diabetes, compared to 149 (7.7% in the placebo group (HR 0.48; 95% CI 0.33, 0.69; p<0.0001).