New Blood Thinner Works as Well as Coumadin Feb. 8, 2005 - Exanta, a new blood thinner, works as well as Coumadin and doesn't require frequent blood testing, two major new studies show.

But the drug's cost - and liver-safety concerns that last year kept the FDA from approving it - may limit its usefulness.

Coumadin is a very, very tricky drug. All kinds of things affect blood concentrations, so patients and their doctors are constantly working to get the dosage just right. Nobody is saying that an alternative wouldn't be welcome. But there is a lot of disagreement over whether Exanta is the right alternative.

Exanta has a lot going for it. It's an oral drug, and unlike Coumadin, people can take it and be sure they're getting the right dose. And the two studies show that the drug works as well as Coumadin in preventing strokes in patients with the heart rhythm problem called atrial fibrillation and in treating serious deep-vein blood clots called deep vein thrombosis.

The studies, both funded by Exanta maker AstraZeneca, appear in the Feb. 9 issue of The Journal of the American Medical Association. AstraZeneca is a WebMD sponsor.

Both studies find that a minority of patients taking Exanta -- 9.6% in one study, 6% in the other -- had increased levels of liver enzymes. That can be a sign of liver damage. Most of the patients with increased liver-enzyme levels saw them return to normal, sometimes without having to stop taking the drug. But there was one death from liver disease. If Exanta is approved - as it is in seven European countries - the researchers suggest that patients be closely watched for signs of liver trouble.

In an editorial accompanying the studies, Victor Gurewich, MD, of Beth Israel Deaconess Medical Center, Boston, notes that Coumadin rarely works as well in real life as it did in these clinical trials. That would mean that Exanta may be even more effective than the study results suggest.