Level 1: Likely reliable evidence

In persons with impaired glucose tolerance or impaired fasting glucose levels and without CVD, rosiglitazone reduces the incidence of diabetes but increases the risk of heart failure, based on the Diabetes Reduction Assessment with Ramipril and Rosiglitazone Medication (DREAM) trial (Lancet. 2006;368:1096-1105). Participants included 5,269 adults older than 30 who were randomized to rosiglitazone (Avandia) 8 mg (4 mg in first two months) or placebo once daily for a median of three years; they were also randomized to ramipril (Altace) vs. placebo. Rosiglitazone was associated with a reduced incidence of diabetes (10.6% vs. 25%, P <.0001, NNT 7), a reduced incidence of combined outcome of diabetes or death (11.6% vs. 26%, P <.0001, NNT 7), and an increased rate of regression to normoglycemia (50.5% vs. 30.3%, P <.0001, NNT 5). Mortality was 1.1% with rosiglitazone vs. 1.3% with placebo (difference not significant). Rosiglitazone was also associated with an increased rate of confirmed heart failure (0.5% vs. 0.1%, P =.01, NNH 250).

Evidence that rosiglitazone reduces the incidence of diabetes does not mean it should be recommended for this purpose. No studies to date have established that pre-threshold treatment of diabetes with medication delays or prevents complications compared with treatment once diabetes is diagnosed. In addition, the only head-to-head comparison of medication (metformin) and lifestyle changes for prevention of diabetes found lifestyle changes to be more effective.

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Ramipril had no significant effect compared with placebo on the incidence of diabetes (17.1% vs. 18.5%) or the combined outcome of diabetes or death (18.1% vs. 19.5%) (N Engl J Med. 2006;355:1551-1562.)