The clot thickens: New anticoagulant challenges warfarin

Blood is thicker than water, they say. Oh, really? What about those rich families who disown their children and leave them nothing? Zilch, Nada. Disowning children is a popular pastime among many cultures to make family trees look like twigs.

In general, though, I do think families stick together like peanut butter and jelly. Perhaps it's the love the binds the family, and maybe blood shouldn’t be so thick.

What happens when the blood clots up in the wrong places?

“Thinning” the blood is a pretty common practice in medicine. (Thinning is a common term for inhibiting blood clot formation.) Over three million Americans have a heart arrhythmia called atrial fibrillation (A-fib). This irregular heart beat can lead to a stroke if a blood clot forms within the heart chamber, and thus many folks with A-fib are on a blood thinner called warfarin (brand name Coumadin).

After heart attack and stroke, venous thromboembolism is the most common cardiovascular disorder– about one million cases a year. A deep venous thrombosis (DVT) is a blood clot in the deeper veins of the legs that can travel up to the lungs to cause a pulmonary embolism (PE), which can be fatal.

These conditions are also treated with warfarin, which is not the easiest thing to manage. Yes, warfarin is well known to be a rat poison (which sounds like “wharf” riddled with rats). In therapeutic doses, it inhibits the clotting mechanism in humans to reduce the risk of strokes in those who have a-fib and to prevent DVT formation.

Warfarin is tricky to manage because many things interact with it. The INR is the lab test we use to see if the warfarin dose is effective. The higher the INR, the less likely a blood clot will form (i.e. thinner blood). The lower the INR, the more likely a blood clot will form. Because the therapeutic window of INR is pretty narrow, only 55-60 percent of patients regularly achieve their targeted INR values on warfarin. So INR levels have to be checked frequently, at least once a month.

Many drugs will increase the INR, which means the blood is thinner and bleeding occurs much more easily.

Vitamin K counteracts warfarin, so eating foods with vitamin K lowers the INR to make blood clots form easier. Vitamin K is found in many healthy foods, in particular green leafy vegetables.

Pradaxa is the newest anticoagulation drug on the block for A-fib (nonvalvular type such as having had a valve replacement) and venous thromboembolism. Unlike warfarin, lab tests are not needed. No INR! That is a cost saver to Medicare and the patient. Moreover, it’s less of a hassle for the patient and health care providers.

Unlike warfarin, this drug doesn’t interact with many medicines. Also, vitamin K doesn’t interfere with Pradaxa, which means less chance of developing a blood clot as well as improving one’s diet by eating more fresh vegetables. Perhaps that’s a reason Pradaxa at 150mg twice a day has been shown to be more effective than warfarin in preventing stroke from a-fib.

Pradaxa costs up to $8 a day ($240 a month)! Also, it’s a twice-a-day drug, and some patients don’t remember to take the second dose (though if it were a beauty or weight loss pill, I bet they’d remember). It can also upset the stomach.

True Blood? Try Thin Blood on HBO. Vampires who suck the blood of anticoagulated victims will bruise and bleed like an extra on Dexter.
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Dr. Hook cracks a joke or two, but he’s a respected physician with an interesting website, drjohnhong.com. Email him with your questions!