A study finding that one drug is better than a commonly used class of drugs at preventing deaths in people with high blood pressure may help change treatment recommendations in the United States, researchers say.

The study found that the drug metoprolol reduced the death rate by 48 percent in comparison to the widely used diuretics called thiazides, researchers said Thursday.Metoprolol (pronounced muh-TAH-pro-lawl) is one of the heart drugs known as beta blockers. These drugs block the stimulating effect of adrenaline on the heart, reducing the rate and the force at which the heart pumps blood through the body and reducing high blood pressure.

The thiazides make up one class of diuretics, which relieve high blood pressure by stimulating the body to expel fluid, thus lowering the total volume of blood in the bloodstream.

This is the first study to show that a beta blocker can prevent more deaths in people with hypertension than can thiazides, said the principal author of the study, Dr. John Wikstrand of Gothenburg University's Sahlgrenska University Hospital in Sweden.

It is therefore likely to require confirmation before being widely accepted, said Dr. Curt Furberg of the Bowman Gray School of Medicine in Winston-Salem, N.C., who was not associated with the study.

Two earlier studies that compared beta blockers and diuretics failed to find any significant difference in the death rate, he said in a telephone interview. The new study is interesting, he said, but "I'm not sure how it's going to be accepted. It's possible we need to test it in a separate study."