Impaired glucose tolerance
The American Agency for Healthcare Research and Quality published a systematic review  in September 2005 that showed aggressive lifestyle modification is beneficial. This appears to be the most comprehensive overview of IGT written, to date. This reported, for instance, that aggressive lifestyle interventions resulted in a significantly lower progression to diabetes compared with metformin (4.8 percent versus 7.8 percent per year; relative risk reduction 0.39, 95% CI 0.24 to 0.51), especially in individuals 60 years of age or older.
The Diabetes primary prevention trial and the Diabetes protection study, large scale European and American studies suggest that when we identify impaired glucose tolerance (IGT), starting metformin is a reasonable idea, with the aim of slowing or avoiding the progression to actual diabetes mellitus.
The DREAM study has established that treating 7 patients with impaired fasting glucose or impaired glucose tolerance by Rosiglitazone for 3 years will prevent 1 from progressing to diabetes so rosiglitazone is likely to be beneficial.  Ramipril did not have such benefit, even if it normalised blood glucose so is unlikely to be benefical.
Whether one can identify insulin resistance (or even IGT!) by eye and whether metformin is justifiable in that case is another matter. At pence per day, and with a small appetite suppressant effect, pretreating with metformin fat people who are not formally diabetic yet is not wholly stupid. Evidence for its effectiveness is deficient and we do not have cost effectiveness analysis yet compared to rosiglitazone. Appropriate lifestyle modification is much more cost effective and as its benefit is sustained, more clinically effective, than any drug on present evidence.
- ↑ Impaired Glucose Tolerance and Fasting Glucose, Diagnosis, Prognosis, and Therapy
- ↑ The DREAM (Diabetes REduction Assessment with ramipril and rosiglitazone Medication) Trial Investigators. Effect of rosiglitazone on the frequency of diabetes in patients with impaired glucose tolerance or impaired fasting glucose: a randomised controlled trial. The Lancet 2006 Published online September 15, 2006 DOI:10.1016/S0140-6736(06)69420-8 accessed 16th September 2006 registration may be required
- ↑ The DREAM Trial Investigators Effect of Ramipril on the Incidence of Diabetes Published at www.nejm.org September 15, 2006 (10.1056/NEJMoa065061) accessed 16 September 2006 registration may be required
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