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Thursday, 30th October 2003
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Exanta™ showed superiority in prevention of thromboembolism
when compared to warfarin.
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A new alternative to the commonly used drug warfarin, shows promising
results. In a study recently published by the New England Journal of Medicine,
Exanta (ximelagatran) manufactured by AstraZeneca®, showed a superior ability
to prevent venous thromboembolism when compared to the standard drug warfarin.
Exanta is an oral direct thrombin inhibitor that does not require monitoring
of coagulation or dose adjustment. This makes exanta easier to use in comparison
to warfarin.
A previous study had already shown that
Exanta was equal in efficacy to warfarin at a dose of 24mg. This study which
included 1851 patients who had undergone total knee replacement, was designed
to show whether giving a high dose of Exanta was superior to warfarin in
preventing thromboembolism.
Exanta was given 36 mg twice daily, starting the morning after surgery,
with warfarin therapy started the evening of the day of surgery. The composite
end point of venous thromboembolism and death from all causes and the incidence
of bleeding were the primary outcome measures
Oral Exanta at a dose of 36 mg twice daily was found superior to warfarin
with respect to the primary composite end point of venous thromboembolism
and death from all causes (20.3 percent vs. 27.6 percent; P=0.003). There
were no significant differences between these two groups with respect to
major bleeding (incidence, 0.8 percent and 0.7 percent, respectively), perioperative
indicators of bleeding, wound characteristics, or the composite secondary
end point of proximal deep-vein thrombosis, pulmonary embolism, and death
(2.7 percent vs. 4.1 percent; P=0.17).
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it reduced the risk of blood clots by one-quarter after knee replacement
surgery (compared to one-fifth for warfarin), and may cut the long-term
risk of another clot developing in patients who had a blood clot in a leg
or lung (twice as much as warfarin).
Warfarin, a widely prescribed drug for the prevention of blood clots, was
first developed as a rat poison at the University of Wisconsin. Professor
Karl Paul Link identified an anticoagulant in spoiled sweet clover while
trying to figure out why cows were bleeding to death after eating it. He
developed it into a rat poison and it was patented in 1948. Warfarin is
still used in some rat poison. At the time, warfarin was considered too
dangerous for humans. Researchers reconsidered after a farmer tried to commit
suicide with it but survived. It was first used as blood thinner in the
1950s.
It is still the only oral blood thinner available to protect against
clots that can block blood vessels. It is widely prescribed after strokes,
heart attacks and orthopedic surgery and is also given to prevent recurring
clots in the legs or lungs. But warfarin, which takes time to kick in, interacts
with other drugs and foods containing vitamin K. It requires regular blood
tests to adjust the dose. Doctors are wary of using it for more than a few
months because of the risk of bleeding. Exanta, also known as ximelagatran,
works by targeting one coagulation factor; warfarin affects many.
One problem that needs to be followed up in future studies of Exanta
was an unexplained increase in liver enzymes. In about 6 percent of the
Exanta group, there was an unexplained increase in liver enzymes, which
has been seen in other studies of the drug. However, levels increased in
the first four months and then returned to normal without any apparent damage
to liver function.
AstraZeneca, which paid for the studies, has filed for approval of Exanta
in Europe and expects to apply for U.S. approval this year. It is not yet
known how much the drug will cost.
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