TABLE 1.

Randomized Clinical Trials Evaluating Metformin for the Prevention of Type 2 Diabetes in High-Risk Individuals

Study (Country, Year of Publication, n)Key Glycemic Eligibility CriteriaDuration of Follow-UpIntervention (n)Diabetes Incidence, by Events (Per 100 Person-Years) or by Cumulative Incidence at Study End (%)Relative Risk Reduction in Diabetes Incidence Compared to Control/Placebo (%)
DPP (United States, 2002, n = 3,234) (3)• FPG 95–125 mg/dL (≤125 mg/dL in American Indian clinics)
• 2-hour glucose after 75 g oral glucose load: 140–199 mg/dL
2.8 yearsMetformin 850 mg BID (n = 1,073)7.8*31*
Intensive lifestyle intervention (n = 1,079)4.8*58*
Placebo (n = 1,082)11.0
IDPP (India, 2006, n = 531) (11)• IGT on two occasions (persistent IGT)30 monthsMetformin 250 mg BID (n = 133)40.5%*26*
Lifestyle modification (n = 133)39.3%*29*
Lifestyle modification plus metformin (n = 129)39.5%*28*
Control (standard health advice) (n = 136)55.0%
CANOE (Canada, 2010, n = 207) (12)• At least one risk factor for type 2 diabetes
• IGT
3.9 yearsRosiglitazone + metformin (2 mg/500 mg combination capsule BID) (n = 103)13.6%*66*
Placebo (n = 104)39.4%
  • * P <0.05 compared to placebo or control. BID, twice daily.