Clinical Health Updates

Metformin does not harm patients with HF and diabetes

Clinical Question:
Do oral hypoglycemics cause harm in patients with diabetes and heart failure?

Bottom Line:
Metformin may decrease mortality in patients with heart failure. Insulin is associated with increased mortality. The thiazolidinediones decreased mortality but increased hospitalization for heart failure.

Eurich DT, McAlister FA, Blackburn DF, et al. Benefits and harms of antidiabetic agents in patients with diabetes and heart failure: systematic review. BMJ 2007;335(7618):497.

Study Design:
Meta-analysis (other)

Up to 40% of adults with diabetes will have heart failure. Diabetes worsens the outcomes from heart failure, and tight control of blood glucose is associated with worse outcomes in patients with heart failure. To investigate the role of antidiabetic agents in patients with heart failure, these Canadian researchers searched several databases for randomized controlled trials or cohort studies that evaluated the association between hypoglycemic agents and clinical outcomes in patients with diabetes and heart failure. Two authors independently selected the studies for inclusion and abstracted the data. Research results for insulin and metformin were not homogeneous and were not formally combined. Three studies found an increased mortality associated with insulin therapy; the fourth and largest study did not find an associated increase in mortality (but did not find a decrease, either). Thiazolidinedione treatment was associated with reduced all-cause mortality (odds ratio [OR] = .83; 95% CI = 0.71 – 0.97), but an increase in hospitalization for heart failure. Metformin as single therapy was associated with decreased mortality as compared with sulfonylureas (OR = .70; 95% CI, 0.54 – 0.91) or insulin (OR = .86; 95% CI, 0.78 to 0.97) after 2.5 years of treatment, as was combination therapy with metformin and a sulfonylurea. Sulfonylureas were not independently studied but were used in comparison groups for several studies of other hypoglycemic drugs. In these studies, there was no increased mortality with sulfonylureas. Most of the studies were of good quality.