People who need to take a blood thinner because they've had a clot in the deep veins of their legs appear to do better with the new drug Pradaxa (dibigatran) than with the older drug warfarin, researchers report.
Long-term treatment of these blood clots is safer and more convenient with Pradaxa than warfarin, the new study found.
Extended treatment with blood thinners after clots develop in the veins or the lungs should be considered more often than it is, said lead researcher Dr. Sam Schulman, a professor in the division of hematology and thromboembolism at McMaster University in Hamilton, Ontario, Canada.
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If a clot in the leg breaks loose and travels to the heart, brain or lungs, it can cause a heart attack, stroke or a pulmonary embolism — all of which can be fatal.
People taking warfarin need periodic blood tests to be sure they aren't getting too much of the drug, which raises the risk of major bleeding, or too little, which is ineffective.
Pradaxa also has a lower risk of bleeding than warfarin, Schulman said, and the bleeding that does occur is less serious than that seen with warfarin, he added.
For the study, published Feb. 21 in the New England Journal of Medicine, Schulman's team conducted two studies of more than 4,000 patients, average age 56, who had clots in the legs, also known as venous thromboembolism. In one, Pradaxa was compared with warfarin, and in the other Pradaxa was compared with placebo.
In the Pradaxa-warfarin comparison, the researchers found that 1.8 percent of patients taking Pradaxa had recurrent clots, compared with 1.3 percent of patients taking warfarin.
Fewer patients taking Pradaxa, however, had major bleeding (13) compared with those taking warfarin (25).
In the study comparing Pradaxa with a placebo, three patients taking the drug developed clots, compared with 37 patients taking placebo.
In this group, two patients taking Pradaxa developed major bleeding, while none in the placebo group did, the researchers added.
The trials were paid for by Boehringer Ingelheim, the maker of Pradaxa.
"These new anticoagulants are great and appear to be as effective as the only other oral one out there, warfarin," said Dr. Jean Connors, medical director of the anticoagulation management service at Brigham and Women's Hospital and Dana-Farber Cancer Institute in Boston.
They do, however, still have the risk of bleeding associated with them, said Connors, who wrote an accompanying journal editorial. "But they are easier to take because you don't need blood tests," she said.
Antidotes to bleeding caused by Pradaxa are in the works, Connors said. "With warfarin, bleeding can be reversed within half an hour, whereas with these drugs there is no good specific reversal for them," she said.
Cost of treatment is a consideration, too. Although Pradaxa is a lot more expensive than warfarin up front, when the associated costs of monitoring are accounted for, the two drugs appear to run about the same, Connors said.
"Warfarin is an extremely cheap drug, costing anywhere from $5 to $10 a month, and co-pays for Pradaxa are anywhere from $25 to $50 a month," she said.
Some cautions may be in order, however. Recently, the U.S. Food and Drug Administration said in a warning that Pradaxa should not be used to prevent stroke or blood clots in patients with mechanical heart valves.
The agency noted that a clinical trial in Europe was halted because patients taking Pradaxa were more likely to suffer strokes, heart attacks and clots forming on their mechanical heart valves than patients taking warfarin.