Five common questions about blood thinners

When most of my patients think of “blood thinners,” they think of coumadin (also known by the brand name warfarin). They also often have preconceptions and questions about these therapies that “thin” the blood to treat or prevent blood clots.

Blood carries all the things our tissues need to survive and delivers them through arteries to the body before returning that blood via veins to repeat the process all over again. In some ways, the vascular system — blood, arteries and veins — is to the body what a modern transportation system is to a city. The difference is that while a traffic jam is annoying, a blockage in the vascular system is a medical emergency. When blood stops flowing to an area of the brain, we call it a stroke; when flow stops to an area of the heart, we call it a heart attack; when flow stops to an area of the lung, we call it a pulmonary embolism. Blockages can form for a variety of reasons; one of those reasons is a blood clot.

Blood thinners, or anticoagulants, have a long and sometimes misunderstood history. The first researchers to discover a substance that reduced blood’s ability to clot were looking for something that would have the opposite effect. Instead, in 1916 while studying dog liver tissue, they found a substance that prevented clotting. They named it after the Latin for liver and called it “heparin.” It was turned into a medicine; however, the new treatment remained limited to hospital settings because it required an intravenous line for administration.

In the time since heparin was first discovered more than 100 years ago, some things have stayed the same. Heparin is still used in hospitals and operating rooms. Some things have changed and lots of new options are available. For instance, coumadin was the first blood thinner that could be taken by mouth (rather than through an injection). Even newer medications have been developed in recent years that allow for more convenient dosing and monitoring.

If you or someone you know has been recommended a blood thinner but is worried about the effect on their lifestyle, try discussing the pros and cons of all the different options with your or their medical provider.

Here are a few answers to questions I hear when talking with patients on the subject:

Isn’t coumadin poison?

The answer is yes when there’s too much. Coumadin is a good thing; too much of a good thing could still be a bad thing. Before being approved for use in humans, it was introduced as a rat poison (at high levels) in 1948. Perhaps even more interesting is that the main component of coumadin was causing health problems for cows even before it was helping humans. The brand name for coumadin is “Warfarin” which comes from an acronym for the Wisconsin Alumni Research Foundation. It turns out that WARF funded a biochemist at the University of Wisconsin in his work to understand why cows were dying of a mysterious bleeding disorder. He linked the deaths back to moldy sweet clover hay and isolated a compound that was named “coumarin” and marketed under the generic drug name “coumadin.”

In high doses, coumadin was poisonous and was initially marketed as a poison at a high dose. Scientists and medical professionals soon realized that, at the right dose, it could save lives by treating or preventing blood clots. Now there was finally a medication that patients could take to treat a blood clot in the veins of the legs or the lungs. The same medication could also be used to prevent blood clots when patients were at high risk of forming them, such as after certain surgeries or with certain abnormal heart rhythms.

If I take coumadin, do I have to stop eating my favorite foods?

When a patient asks me if they need to stop eating green leafy vegetables or other favorite foods the answer is no, but a consistent diet is important.

For many years the mechanism by which coumadin stopped clotting was not fully understood. Eventually, scientists discovered that it works by blocking vitamin K, which the liver uses to make several proteins that modulate the way blood clots are formed. As humans, we don’t make our own vitamin K. Instead, we get it in our food and from the healthy bacteria in our gut. That is why things like diet and antibiotics can magnify or diminish the effect of coumadin.

Consistency of diet is important, but we can dose coumadin according to whatever consistent diet a patient prefers. It also means that patients don’t need to avoid medications like antibiotics but should let their prescribing provider and/or monitoring pharmacist know when their medication regimen changes.

Do I need to get frequent blood tests while on coumadin?

That depends on what you consider frequent, but generally, the answer is yes. Most medicines have a “Goldilocks” effect – too little isn’t helpful and too much is harmful. When dosing coumadin we use a blood test to check that we have the dose just right. If the dose is too low, we can increase it. If the dose has been too high, we may hold a few doses and then reduce it. In rare cases, we may even use a reversal agent such as vitamin K to correct a significant imbalance.

When first starting the medication, we usually check a bit more frequently, but after patients have a consistent routine and their labs have been stable, we space out the testing. Still, patients should get testing every several weeks and occasionally check blood counts to monitor for signs of undetected bleeding.

So, if my diet is inconsistent and I don’t want to get frequent blood tests, I can’t take a blood thinner?

Not the case! The science of anticoagulation has come a long way in the more than 100 years since heparin was first discovered. Newer medicines like dabigatran, rivaroxaban and apixaban take a more direct route to inhibit clot formation. They don’t require regulation of vitamin K intake in the diet and don’t have as many medication interactions as coumadin. They also don’t require the same blood testing that coumadin requires.

There are a number of reasons your situation might be better suited to one type of anticoagulant or another. For example, the newer blood thinners are more expensive. However, many patients find the convenience worth the added cost. There are also some situations in which we would not use them, such as with reduced kidney function. Also, since they are newer, we are still learning how to dose them at very high or very low weights. We also don’t have as much experience with reversing the newer medications, which can come up in some emergency medical situations. Talk to your provider about your options.

If I start a blood thinner, will I have to take it forever?

That depends. Sometimes the conditions that put a patient at risk for forming a blood clot are temporary, like the period after a surgery or an injury, and we can stop the medicine once the risky period is over. When a first blood clot is diagnosed, we usually treat for a set period of time, discontinuing when that period is complete. There are other times when we expect that a patient will be at high risk for a blood clot indefinitely. Examples include patients who have had more than one blood clot or have a heart rhythm that increases the risk for clot formation. In these cases, we treat indefinitely or until the risks of the medication outweigh its benefit.

Whatever the reason a blood thinner has been recommended, we have the flexibility to find a medication that works for each individual situation. A conversation with your clinician can help to find the option that is best for any patient.

Peter Barkett, MD, practices internal medicine at Kaiser Permanente Silverdale. He lives in Bremerton.

This article originally appeared on Kitsap Sun: Five common questions about blood thinners