"This is clearly a setback," said Dr. Alan Go, associate director for clinical research at Kaiser Permanente of Northern California, co-author of an accompanying editorial in the journal.
Go, like other experts in the field, acknowledged that "we are eager to find a replacement for warfarin. It is a remarkably effective drug but challenging to deliver and challenging to take."
Buller said that if all turns out as well as he hopes, idraparinux could be a useful alternative for many people who could get the needed anti-clotting activity with a single weekly injection, while forgoing the constant blood tests required for warfarin users.
"That might lead to some effective agent," Go said. "It's certainly possible, and I wouldn't rule it out. But we would need another large trial to prove it."
Idraparinux is not the only anti-clotting medication in the race to supplant warfarin, Go noted. "At least two oral inhibitors are being tested," he said. "There are different approaches to affecting clotting factors, and there is a very aggressive drive to find something to replace warfarin."
Buller said: "The primary question is, can this drug replace warfarin in preventing stroke? The answer, I think, is yes, but not in subgroups of individuals."
You can learn about the role of anti-clotting drugs in preventing strokes from the Heart Rhythm Society.
SOURCES: Harry R. Buller, M.D., chairman, department of vascular medicine, Academic Medical Center, Amsterdam, the Netherlands; Alan Go, M.D., associate director for clinical research, Kaiser Permanente of Northern California, Oakland; Jan. 26, 2008, The Lancet
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