But this drug may not be worth the risk, said Dr. Marcel Levi of the University of Amsterdam and colleagues at Novo Nordisk.

Their **ysis of 35 studies found that the overall likelihood that an artery would clog was 68 percent higher with NovoSeven therapy compared to a placebo.

The risk of heart attack, angina or related complication more than doubled, the researchers reported in the New England Journal of Medicine .

People over 65 who got the drug were more than twice as likely to develop an unwanted clot in an artery than younger patients, they found. Those over 74 were three times more likely.

"This is a highly effective drug in patients with excessive blood loss in various circumstances. But the main message is you need to realize that there is a price to be paid," Levi said in a telephone interview.

"If a patient's bleeding so serious he or she may have a major problem or even die, you can accept the small increased risk of having an arterial thrombosis (clot)," Levi said.