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Another warfarin alternative for stroke prevention in people with a-fib

To switch or not is a decision for you and your doctor to make.

Warfarin’s long reign as the drug for preventing stroke in people with atrial fibrillation is being challenged by the second new blood thinner to come on the market within the span of less than a year.

Rivaroxaban (Xarelto) prevents blood clots — and the strokes arising from them — by blocking formation of thrombin, a protein that forms a netlike trap for red blood cells. Warfarin (Coumadin, generic) does its job by blocking the liver’s production of clot-promoting proteins.

The relationship between strokes and atrial fibrillation, a common rhythm disorder of the heart’s upper chambers, is compelling: Up to one-quarter of all clot-caused (ischemic) strokes can be attributed to atrial fibrillation. Those strokes are fatal 20% of the time, and 60% of people who survive one end up severely disabled. Clot-preventing medications significantly reduce clot formation and the chances of a stroke.

Warfarin has been effectively preventing strokes in people with atrial fibrillation since the early 1950s, despite the inconveniences of taking it. Those hassles include the need for frequent monitoring and dosage adjustments and the drug’s inconsistent effects in response to certain foods (especially green leafy vegetables) as well as vitamins, supplements, and other drugs. Xarelto is hassle-free in these regards.

The FDA based its approval of Xarelto on a clinical trial known as ROCKET-AF. This study found that among more than 14,000 people with atrial fibrillation, rivaroxaban was as effective as warfarin at preventing clot-caused strokes and no more likely than warfarin to cause excessive bleeding, a pitfall to which all blood thinners are prone. But Xarelto was less likely than warfarin to cause bleeding in the brain (hemorrhagic stroke) and bleeding episodes that resulted in death (New England Journal of Medicine, Sept. 8, 2011).

Warfarin, Pradaxa, and Xarelto: Head to head to head

Blood thinner

Effectiveness for stroke prevention

Out-of-pocket cost

Risk of brain bleeding

Convenience

warfarin (Coumadin, others)

Highly effective

Inexpensive

Higher than with Pradaxa or Xarelto

Requires frequent monitoring and dose adjustment

dabigatran (Pradaxa)

More effective than warfarin

More expensive than warfarin

Lower than with warfarin

No monitoring required

rivaroxaban (Xarelto)

As effective as warfarin

More expensive than warfarin

Lower than with warfarin

No monitoring required

No death knell for warfarin

The approval of Xarelto came less than a year after the FDA approved dabigatran (Pradaxa). With these two alternatives now available for stroke prevention in people with atrial fibrillation — and a third (apixaban) that may be approved soon — has warfarin outlived its usefulness? No.

While the two new drugs are more convenient to use and seem less likely to cause brain bleeding, only time will tell whether unforeseen side effects and risks crop up as more people use them. They are also more expensive than warfarin; out-of-pocket cost for either of the new drugs will likely be several times that of warfarin. That alone may rule out a switch for some people.

Also, accidentally missing a dose of warfarin may not be as risky as forgetting to take a dose of the other two drugs. Because blood levels of Xarelto and Pradaxa drop more quickly than those of warfarin, a missed dose of one of the new drugs means more rapid loss of stroke protection.

In addition, some doctors think that the frequent monitoring required with warfarin use may actually motivate people to take it as directed. Monitoring also exposes warfarin users to regular visits with health professionals, which may benefit people with atrial fibrillation.

Unanswered questions

If you opt for one of the new alternatives, be aware that doctors aren’t experienced yet in how best to change over from warfarin, although detailed instructions for transitioning are provided in the package inserts for both Xarelto and Pradaxa.

The most important unanswered question is how to quickly reverse the blood-thinning action of the two new drugs in case of a bleeding emergency. With warfarin, a simple injection of vitamin K usually does the trick.

People currently on warfarin who are thinking about switching and those with newly diagnosed atrial fibrillation who need to take a blood thinner should have a comprehensive conversation with their doctors about this important but very personal choice. If you do opt for one of the new drugs, pay attention to any future reports of adverse effects.

Posted by: Dr.Health

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