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.


Don’t Be Scared by (or of) Statistics

A study came out recently showing that having a joint replaced increases the risk of having a heart attack by at least a factor of three in the month after surgery. Gah! What’s a person to do, then, if you’re barely able to walk because your knee or your hip is causing you so much pain? The first thing to do is look at the actual numbers behind those statistics.

How Large Is Large?

Researchers in Great Britain reviewed records of patients through the Health Improvement Network, which captures information about more than 10 million people. They found that during the period 2000–2012, nearly 14,000 people in that database had a total knee replacement, and more than 6,000 had a total hip replacement. When compared to similar patients who had not had a joint replaced, those who had a new knee were more than 8 times as likely to have a heart attack in the following month, and those with a new hip were more than 4 times as likely to experience a heart attack.

Those figures sound dreadful, but the raw numbers were so low that the change in absolute risk is negligible. And over the longer term, the risk of heart attack evened out between the two groups. In the 4 years following surgery, there were 306 heart attacks in the replacement knee group and 286 in the born-with knee group. For the hip folks the numbers were 128 and 138 (yes, fewer in the replacement group). For the knee group those 20 extra heart attacks sent the total risk zooming from 2.0% without replacement all the way up to 2.2% with joint replacement. Hardly a cause for excitement. And in a group that was older (average age 71) and heavier (BMI of 28—not obese but still overweight) to begin with, it’s not surprising that there were heart attacks.

What, Me Worry?

Other recent studies had shown a reduced risk of heart attack long-term in those who have had a joint replaced. Research in Toronto showed that over a followup period averaging 7 years, joint replacement reduced a person’s risk of heart attack, stroke, or other cardiovascular events by about 12%. Other research, conducted in Taiwan, showed a 7% reduction in CV risk over 5 years.

There could be many reasons for this health improvement. It could come from a change in diet after surgery, or less for NSAID pain medication, or increased physical activity. Regardless, the benefit is there.

The press release from the publisher of this current study was titled, “Knee and Hip Replacements May Be Bad for the Heart.” This seems like a title aimed at getting noticed rather than one that tells the truth. Now that you’ve seen how statistics get cherry-picked to make a point, you can be a smarter consumer of information.