Blood thinners are among the top drugs prescribed by cardiologists, and they are taken by millions of Americans every day. By targeting pathways involved in coagulation, blood thinners reduce the formation of blood clots that could lodge in a blood vessel and cause a stroke, heart attack, or blockage.
These drugs are prescribed for patients with mechanical heart valves, after cardiac surgery, and for conditions that weaken contraction of the left ventricle, such as scar tissue following a serious heart attack. The main indication, however, is atrial fibrillation (A-fib).
A-fib is the most common type of cardiac arrhythmia. Normally, the upper chambers of the heart contract in unison in response to signals from the sinus node. In patients with A-fib, this response is overpowered by electrical signals scattered throughout the atria, or upper chambers of the heart. Instead of contracting, the heart vibrates rapidly. This allows blood to pool in the atria and raises the risk of blood clots. Blood thinners reduce this risk by discouraging clotting.
There are two main types of blood thinners: Coumadin (warfarin) and non-vitamin K oral anticoagulants (NOACs).
Coumadin: The Drug Patients Love to Hate
First approved in the 1950s, Coumadin has been the primary blood thinner prescribed by doctors for decades. It works by blocking the production of clotting factors in the blood that are dependent on vitamin K, the “clotting vitamin.”
If you’re on Coumadin, you need to get frequent blood tests to monitor prothrombin time, or the time it takes for a clot to form. If your number is too low, the risk of clotting increases. If it’s too high, there’s an elevated risk of bleeding. Both can cause serious adverse effects, including stroke and internal bleeding.
There are also dietary restrictions for patients on Coumadin, particularly concerning leafy greens and cruciferous vegetables, which are rich in vitamin K. It’s not that you can’t eat these foods, but your intake should be consistent to keep vitamin K levels on an even keel.
Coumadin also interacts with a large number of other drugs, which may reduce its effectiveness or increase the risk of bleeding. It can interact with a handful of supplements as well, including Ginkgo biloba, ginseng, garlic, dong quai, St. John’s wort, vitamin K2, and high-dose vitamin E.
Can You Replace Coumadin with a NOAC?
In the past few years, a newer class of drugs—called non-vitamin K oral anticoagulants (NOACs)— has overtaken Coumadin as the blood thinner of choice for many patients with A-fib. However, for those with a mechanical heart valve or moderate to severe mitral valve stenosis (narrowing), Coumadin is still the best treatment.
The most common NOACs include:
- Eliquis (apixaban)
- Xarelto (rivaroxaban)
- Pradaxa (dabigatran)
- Savaysa (edoxaban)
Unlike Coumadin, NOACs do not require regular blood tests. They don’t act on vitamin K pathways, so they are not affected by vitamin K in foods. Plus, compared to Coumadin, they also have a lower risk of causing bleeding, including brain bleeds that can cause hemorrhagic strokes.
As for efficacy, in 2019 the American Heart Association, American College of Cardiology, and Heart Rhythm Society updated their guidelines for the treatment of atrial fibrillation to recommend NOACs for most A-fib patients who require a drug to reduce their risk of stroke.
An initial concern about NOACs when they first came out was that there was no “reversal agent” to control bleeding in the event of an overdose, adverse reaction, or an accident or emergency surgery that caused excessive bleeding. Reversal agents are now available, so that is no longer a concern.
Although NOACs have few drug interactions compared to Coumadin, aspirin, ibuprofen, and the SSRI antidepressants paroxetine and sertraline should be used with caution, as they may increase bleeding risk. NOACs are also reported to have possible interactions with several supplements, in particular Chinese herbs, Ginkgo biloba, St. John’s wort, ginseng, and ginger.
Potential Side Effects of Blood Thinners
All blood thinners, including NOACs, have potential side effects:
- Easy bruising and/or bleeding gums
- Gastrointestinal bleeding
- Slower healing wounds
- Weakness, cold sensations, itchy skin, fever, and abdominal discomfort
- Hemorrhagic stroke
Serious adverse effects are more common in individuals who are age 75 or older, have a history of kidney problems or gastrointestinal bleeding, or are taking aspirin, ibuprofen, or other drugs that increase the risk of bleeding.
Regardless of the drug you are taking, it is important to monitor your meds closely, as excessive bleeding can occur when you take too much of any blood thinner.
Are There Natural Alternatives to Blood Thinners?
I got this question a lot back when Coumadin was the only game in town, though less often now that many patients are on the more convenient and better-tolerated NOACs. Yet, my answer is the same as it has always been.
For most patients with A-fib, NOACs are recommended. The most recent studies reveal that the drug’s benefits—reducing the likelihood of having a stroke—outweigh the risks. Patients with a prosthetic heart valve or moderate to severe mitral stenosis need to be on Coumadin for stroke prevention. NOACs are not recommended.
What about natural alternatives? The only patients who could potentially opt for natural therapies are those who have "lone" A-fib. That means they have atrial fibrillation but with normal valve function and left atrium size. Because these patients have a lower risk for blood clots, they may be good candidates for natural blood thinners such as:
- Omega-3 fatty acids from fish, squid, or krill oil (2–3 grams daily)
- Nattokinase (100 mg daily)
- Vitamin E as mixed tocopherols (100–200 IU daily)
- Lumbrokinase (20 mg daily)
- Garlic (1–2 grams daily in capsule form)
It is Critical to Work Closely with Your Doctor
If you are taking any type of blood thinner, talk to your doctor about potential interactions and pay close attention to signs of bleeding such as unusual bruising, bleeding gums when you brush your teeth, and dark or bloody stools.
Blood thinning medications can be lifesaving! So, always take your medication as directed at the same time every day, and do not discontinue it without consulting with your physician first.