Treatment Is Found for Recurring Blood Clots

Steady low doses of an old-fashioned blood thinner have been shown to dramatically lower the risk of recurring blood clots in the legs and lungs, offering the first effective treatment for an estimated 750,000 Americans annually.

Until now, there has been no accepted long-term therapy to prevent these sporadic clots from coming back, as they often do. The study, released Monday, found that a modest dose of the drug warfarin reduces this risk by two-thirds.

Warfarin, also known as Coumadin, is already the standard blood thinner for treating these clots. Typically, though, the medicine is stopped after a few months because of concern that the standard dose will trigger bleeding.

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 said.

The American Heart Assn. estimates that each year, about 2 million people suffer a deep-vein thrombosis, a clot in a vein deep in the leg. The result is painful swelling that becomes life-threatening if the clot floats to the lungs.

More than half of all cases 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.

Ridker’s study compared low-dose warfarin and placebos in people at risk for these recurring clots. It 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.