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Insulin-Metformin Combo Tied to Poorer Survival

Other experts dispute the study's conclusions

WebMD News from HealthDay

By Steven Reinberg

HealthDay Reporter

TUESDAY, June 10, 2014 (HealthDay News) -- The combination of metformin and insulin for people with type 2 diabetes may slightly increase death rates among patients, according to researchers from Vanderbilt University.

However, other experts question the study's conclusions and claim it is at odds with other better-designed studies that show the combination of metformin and insulin is both safe and effective.

"Insulin remains a reasonable option for patients who have very high glucose [blood sugar] or who desire flexible and fast blood sugar control, but most patients taking metformin prefer to delay starting insulin," said lead researcher Dr. Christianne Roumie, an associate professor of internal medicine and pediatrics at Vanderbilt University in Nashville, Tenn.

"The current study suggests that adding a sulfonylurea to metformin should be preferred to adding insulin for most patients who need a second diabetes drug," she said. Sulfonylureas include glibenclamide (Micronase), glimepiride (Amaryl), glipizide (Glucotrol) and others. They work by stimulating the body to make more insulin.

Roumie's team found that, compared with those who added a sulfonylurea, those who added insulin to metformin had 30 percent higher odds of heart attack, stroke and death from any cause during the study period. "Although new heart attacks and strokes occurred at similar rates in both groups, mortality was higher in patients who added insulin," she said.

Roumie said she doesn't know why the rate of deaths was higher among study patients taking insulin. "We have a number of studies planned to examine possible mechanisms. We are investigating type 2 diabetes outcomes associated with blood sugar swings and with episodes of hypoglycemia (low blood sugar) tied to insulin," she said.

Sulfonylureas can also cause low blood sugar levels, according to the American Diabetes Association.

The report was published June 11 in the Journal of the American Medical Association.

For the study, Roumie's team compared the outcomes among people receiving metformin and insulin with those taking metformin and sulfonylureas.

Using U.S. Veterans Health Administration (VA), Medicare, and National Death Index data, they compared the risk of heart attack, stroke, or all-cause death between the different therapies. Among more than 178,000 people taking metformin, almost 3,000 added insulin and nearly 40,000 added a sulfonylurea.

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