July 1 (HealthDay News) -- Results from a new trial have dashed hopes that early use of two blood pressure drugs could slow the loss of kidney function caused by type 1 diabetes.

But the study, reported in the July 2 issue of the New England Journal of Medicine, does find benefits for the drugs against diabetes-caused eye damage.

Type 1 diabetes, the less common form of the disease, results from the body's failure to produce insulin and usually is diagnosed early in life. The two drugs in the trial, enalapril (Vasotec) and losartan (Hyzaar), are commonly prescribed to slow the kidney damage caused by the disease, said Dr. Michael Mauer, a professor of pediatrics and medicine at the University of Minnesota and lead author of the study.

"They are widely used at later stages of the disease, when it is well established," Mauer said. "Some physicians have been willing to extrapolate to treat at very early stages of the condition, but no studies such as ours had been conducted."

The trial included 285 people who had been treated for type 1 diabetes for an average of 11 years. Current practice, Mauer said, is for use of the two drugs to begin about 15 years after diagnosis.

Participants were assigned to take daily doses of a placebo -- an inactive substance -- or either enalapril or losartan. Each acts in a different way to counter the effects of angiotensin, which raises blood pressure by tightening arteries.

After about five years, detailed measurements of kidney function showed no difference in the damage seen in the three groups, the report said.

"From the kidney perspective, it was more of a disappointment than a surprise," Mauer said. "We were more pleasantly surprised by the eye component of the study."

Eye damage was reduced by 65 percent among the participants taking enalapril and by 70 percent among those who took losartan, compared with people in the placebo group.

And so, Mauer said, "the data in the paper support starting this therapy in people who have early diabetic eye changes." Diabetes is a leading cause of vision loss, he noted.

But he added a word of caution. Both drugs can cause fetal damage so they should not be prescribed for women of child-bearing age, he said.

"Other than that, they have a remarkable safety profile," Mauer said.

The study was funded by Merck, which makes both drugs, along with the U.S. National Institutes of Health and the Canadian Institutes of Health Research.

Mauer said that the study results should not affect current use of the drugs in later stages of type 1 diabetes. "They are commonly used for people who already have signs of kidney disease," he said. "They have been shown to have more effective blood pressure effects than other drugs, and they seem to have additional advantages in slowing the progression of kidney disease."

The findings, though, are limited to type 1 diabetes, he said. "I'd be uncomfortable extrapolating from our study to type 2 diabetes," Mauer said. Type 2 diabetes, the more common form of the condition, generally occurs later in life as the body progressively produces less insulin.

SOURCES: Michael Mauer, M.D., professor, pediatrics and medicine, University of Minnesota, Minneapolis; July 2, 2009, New England Journal of Medicine