Nevertheless, doctors wrote 21 million prescriptions for the anti-coagulant Coumadin (generically known as warfarin), a drug growing 5% a year.

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The effects of an anti-coagulant and a death-inducing poison are relatively obvious.

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"It's used particularly for open-heart surgery, where you need immediate control of the anti-coagulant, " says Jack Ansell, vice chair of clinical affairs at Boston University Medical Center.

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Since Xarelto is an anti-coagulant with effects similar to warfarin, and warfarin has been shown to be of little use in ACS, why test it at all?

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In the meantime, DuPont AIDS drug Sustiva fits in with Bristol's two HIV treatments, and DuPont anti-coagulant Coumadin meshes with Bristol's existing heart drugs, even though no patent protects it.

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Eliquis was the first anti-coagulant to prove that it reduced the risk of death compared to warfarin, which has been the standard of care for preventing strokes in patients with atrial fibrillation, a common heart rhythm disorder, for seven decades.

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