Convenient Isn’t Always Best

It seems like everywhere you look these days you see ads for anticoagulant drugs. These meds, Pradaxa, Xarelto, and Eliquis, are being promoted to reduce the risk of stroke due to the heart condition atrial fibrillation (aFib). They’re intended to replace the older warfarin (Coumadin), and are supposed to be better because they’re more convenient. But once you know the facts you’ll see that “convenient” may not be right for you.

No Salad for You Today

Warfarin reduces blood’s ability to clot by blocking the action of vitamin K—a factor in what’s known as the clotting cascade. The drug has been around since the 1950s, and works very well at thinning the blood. It has a bad reputation among patients, though, for two reasons. The first has to do with what’s known as the therapeutic index. This is the range of dosage that walks the line between too little to be effective and so much that it’s dangerous. The balance is so delicate that the brand-name drug was alone in the marketplace for more than 40 years before makers of generics could show that their warfarin was as stable as the branded medication.

Patients on warfarin need regular testing of their blood’s clotting ability, with a test called the INR (international normalized ratio, what used to be known as PT/prothrombin time). When beginning a regimen of warfarin, it can takes weeks of constant testing and adjustment to get just the right dosage. And any change in your other medications or your lifestyle can drag you back into the test/adjust phase.

This leads to the second reason. Warfarin works through the vitamin K system, so you have to keep your dietary intake of vitamin K steady. That is, if you have a salad for dinner, you have to have one pretty much every day, with the same kind of greens. (Leafy greens such as lettuce and kale are the main source of dietary vitamin K.) For just about everyone, the only way to keep your intake constant is to make that intake zero. And, um, leafy greens are good for you.

There’s So Much Blood

The risk of any blood thinner is that of excess bleeding. If you’re going in for surgery you need to stop the medication some time beforehand to avoid excessive bleeding during the procedure. And any injury poses a higher risk. I once watched a friend taking warfarin bleed almost all day from a simple shaving cut. Bumps and falls carry a higher risk of bruising. Serious injuries like those from an auto accident can cause death by bleeding out. The highest risk, though, comes from undetected bleeding such as from an ulcer.

Fortunately, for someone who’s taking warfarin there’s an antidote: vitamin K. But the newer drugs work differently, and there’s no antidote. The results are about what you’d expect. Between 2010 and 2014, there were about 9,000 anti-coagulant-related deaths reported to the FDA. Of those, only 700 were related to warfarin, even though up to 10 times as many patients are taking warfarin as are on these newer drugs. Curiously, studies on the new drugs show a lower risk of stroke compared to warfarin. But the real world doesn’t always agree with results from clinical studies.

Ads for these newer anticoagulants show people leading carefree lives, I suppose because they’re no longer burdened with all the testing. Somehow the family sitting around after a funeral doesn’t make it into those ads.

Oh, and by the way, a 90-day script of generic warfarin costs about $10, while the new guys are $500–$1,000. So much for controlling health care costs.