The finding gives doctors a safe, long-term treatment for deep-vein thrombosis, which occurs when a blood clot forms — usually in the veins in the legs — and causes pain and cramps. If the clot breaks off and lodges in the lungs, it can be fatal.
The condition is also known as “economy class syndrome” because it can appear in airline travelers who sit for a long time in cramped quarters.
Until now, there has been no accepted long-term therapy to prevent these sporadic clots from coming back. This study, released Monday, found that a modest dose of the drug warfarin reduces the risk of another clot by about two-thirds.
Warfarin, also known as Coumadin, is already the standard blood thinner used to treat these clots once they occur. Typically, though, the medicine is stopped after a few months because of concerns that it will trigger bleeding. To prevent another clot, patients in this study took less than half the dose that would ordinarily be given to treat deep vein thrombosis.
Dr. Paul Ridker of Boston’s Brigham and Women’s Hospital, who directed the federally sponsored study, said the treatment costs pennies a day and is easy to administer once the correct dose is determined for each patient.
“It provides an immediate new standard of care, because the current standard is no care,” Ridker told the Associated Press. “Physicians should strongly consider switching their patients to long-term treatment to prevent these clots.”
The drug is initially time-consuming for doctors to prescribe, since they cannot easily figure out how much to give. Two people the same size, sex and age may require vastly different doses to achieve the same result. Doctors set the dose by testing the drug’s effect on patients’ blood clotting. In this study, doctors checked patients’ clotting once every two months once the correct dose was set.
Even with the new results, some doctors questioned whether warfarin will be widely used to prevent clots.
“I think there is a lot of resistance in the medical community to using warfarin. It’s not an easy drug to use. Patients have to get regular blood tests. There is a fear of bleeding,” Dr. Ira S. Nash, associate director of the cardiovascular institute at Mount Sinai Medical Center in New York City, told the AP.
Ridker said a larger problem is that no pharmaceutical company will promote this new use, since the drug is generic. “If it doesn’t become the standard of care, it will only be because there aren’t people out their educating doctors, so to speak,” he told the AP.
More than half of all cases of deep vein thrombosis result from surgery or trauma, such as broken bones, and are not likely to recur. However, Ridker estimates that 750,000 people each year have a deep vein thrombosis resulting from more obscure causes, often an inherited tendency to spontaneously form unwanted clots. Almost a third of these people get another clot within eight years.
Of the 508 people in Ridker’s study, those who received warfarin had a 64 percent lower risk of another clot, compared to those taking a placebo.
The study began in 1998 and was scheduled to end in 2005. However, the early results were so dramatically positive that researchers decided it would be unethical to continue giving people placebos, so the study was stopped in December.