The New Blood Thinners

The NOAC drugs - substitutes for Coumadin

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If you watch any TV, odds are you have been seeing commercials for new anticoagulant drugs (blood thinners) called Pradaxa, Eliquis, Xarelto, and Savaysa. The commercials claim these drugs are easier to take, are safer, and are just as effective (if not more effective) than Coumadin (warfarin).

While these claims are nearly true, they do not tell the whole story.

The Problems With Coumadin

For patients who need to take anticoagulant drugs (for instance, people with atrial fibrillationdeep venous thrombosis, or pulmonary embolus), for many years the only effective option was Coumadin.

Using Coumadin safely and effectively can be a real challenge. It is often necessary to have frequent blood tests to measure coagulation status (the "thinness" of the blood), and frequent dosage adjustments are often required to keep the coagulation status in the correct range. Changes in health, and even eating the wrong foods, can make the blood “too thin” (which can increase the risk of serious bleeding), or not “thin enough” (which can increase the risk of blood clots). At best, taking Coumadin is quite an inconvenience.

The drugs featured in all those commercials are from a new class of drugs that, in many patients, offer an alternative to Coumadin. Doctors often refer to these drugs as the NOACs - “novel oral anticoagulants.”

How The NOACs Work

Anticoagulant drugs work by inhibiting the coagulation factors (also called clotting factors) in the blood. Clotting factors are a series of proteins that work in conjunction with blood platelets to produce blood clots.

Coumadin works by inhibiting vitamin K, the vitamin necessary for the synthesis of several important clotting factors. In fact, giving vitamin K is an effective way to quickly reverse the effect of Coumadin.

The NOACs work by directly inhibiting specific clotting factors. Pradaxa (dabigatran) directly inhibits thrombin, also called clotting factor IIa.

The other available NOACs - Xarelto (rivaroxaban), Eliquis (apixaban), and Savaysa (edoxaban) - work by inhibiting a different clotting factor, factor Xa.

What Makes the NOACs “Better” Than Coumadin?

The NOACs have a major advantage over Coumadin. Namely, they produce a stable anticoagulant effect with standard dosages, so no blood tests or dosage adjustments are required. And there are no dietary restrictions associated with taking NOACs. So taking NOACs tends to be far less disruptive to life than taking Coumadin.

Furthermore, clinical studies suggest suggest that the NOACs are as effective as Coumadin in preventing blood clots. And the risk of major bleeding complications with NOACS appears to be no higher than with Coumadin (and may even be lower).

What Are The Drawbacks To NOACs?

Perhaps the chief disadvantage is that, in contrast to Coumadin, no antidote is currently available for three of these drugs to rapidly reverse their anticoagulant effects. This means that if a major bleeding episode does occur, the potential for a bad outcome may be higher than with Coumadin.

In October, 2015 the FDA approved the new drug Praxbind (idarucizumab) to reverse the effects of Pradaxa. The availability of an antidote to Pradaxa is an important development. However, since the other available NOAC drugs inhibit factor Xa, and not factor IIa like Pradaxa, Praxbind does not reverse their effects. Antidotes to the factor Xa inhibitors are being developed.

Pradaza and Eliquis require twice a day dosing, unlike the Xarelto and Savaysa (and Coumadin) which only have to be taken once a day.

The NOACs are significantly more expensive than Coumadin, and the cost can be prohibitive for patients whose insurance does not cover them.

The NOACs are not approved for some uses, for instance, in patients with artificial heart valves or who are pregnant.

These drugs are mainly excreted by the kidneys, and need to be used with great caution, if at all, in patients with kidney disease.

Finally, since NOACs are indeed quite new, it is relatively likely that as they come into widespread usage, some new, currently unidentified side effects may become apparent. (This is a risk one takes, of course, with any relatively new drug.)

When Should NOACs Be Used?

Frankly, this is a question which medical experts are just now sorting out. But because of the well-known drawbacks of Coumadin, most experts are leaning fairly strongly toward recommending the newer anticoagulant drugs as the first choice in most patients who need chronic oral anticoagulation.

Most such patients will probably find their doctors recommending one of the new drugs if they're being started on anticoagulation for the first time, if they've had difficulty maintaining a stable dose of Coumadin, or if (after listening to the potential risks and benefits of all the choices) they themselves express a clear preference for the newer drugs. On the other hand, patients who've been taking Coumadin successfully — with stable blood tests on a stable dosage — for a few months or longer are probably better off sticking with Coumadin.


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Patel MR, Mahaffey KW, Garg J, et al. Rivaroxaban versus warfarin in nonvalvular atrial fibrillation. N Engl J Med 2011; 365:883.

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