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 not unreasonable, they do not tell the whole story.

The Problems with Coumadin

For people who need to be treated with anticoagulant drugs for more than just a few days (for instance, people with atrial fibrillation, deep venous thrombosis, or pulmonary embolus ), until recent years the only real option was Coumadin.

And this often presented a problem, because using Coumadin safely and effectively can be a real challenge. People taking Coumadin are likely to need frequent blood tests to measure coagulation status (the “thinness” of the blood), and repeated dosage adjustments are often required to keep their coagulation status in the correct range. Changes in their health status, taking over-the-counter drugs, having a few drinks, and even a change in their diet, can make their 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 new drug thinners featured in all those commercials are from a new class of drugs that, for many people, offer an attractive 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 as a class have one major advantage over Coumadin. Namely, they produce a stable anticoagulant effect with standard dosages, so no blood tests or dosage adjustments are usually required. And there are no dietary restrictions associated with taking NOACs. So taking NOACs tends to be far less disruptive to a person’s life than taking Coumadin.

Furthermore, clinical studies 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?

During their early years in clinical medicine, perhaps the chief disadvantage of NOACs was that, in contrast to Coumadin, no antidote was available to rapidly reverse their anticoagulant effects. So if a major bleeding episode occurred with these drugs, the potential for a bad outcome was higher than with Coumadin.

However, in 2015 the FDA approved the new drug Praxbind (idarucizumab), which can reverse the effects of Pradaxa. More recently AndexXa (andexanet alpha) was approved as a reversal agent for the factor Xa inhibiting NOAC drugs. The recent availability of these agents is expected to reduce the risk of permanent damage or death caused excessive bleeding with NOAC drugs.

Pradaxa and Eliquis require twice a day dosing, unlike 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 people whose insurance does not cover them.

The NOACs are not approved for some uses, for instance, in people 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 newer drugs, it is possible that additional, 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 still 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 many people who need chronic oral anticoagulation.

A Word from Verywell

The NOAC drugs offer a viable alternative to Coumadin for people who need chronic anticoagulation therapy. For many, NOACs are quite an attractive option.

People are likely to 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, people 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, as are those whose insurance will not yet cover these expensive new drugs.

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Article Sources

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