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Anticoagulants & Blood Thinners: How Do They Work?

Starting an anticoagulant, more commonly referred to as a “blood thinner,” can be quite intimidating for most patients. Why do I need to be on a blood thinner? Will I bleed? What is the best option for me? These are some of the questions that patients ask. Here we will discuss some of the common reasons to be on anticoagulation therapy, which medication might be the best option for you, and common concerns.

What Are Anticoagulants For?

Anticoagulants are used to treat or prevent clotting of blood that can block a vein or artery, which may lead to heart attack or stroke. The most common reasons to be on anticoagulant therapy are history of deep vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation (a-fib),  the presence of an artificial heart valve, or recent joint replacement surgery. Your doctor can help determine if/when you should start on an anticoagulant based on indication and other risk factors such as history of stroke, age, high blood pressure, and diabetes.

How Do Anticoagulants Work?

There are a series of reactions that happen in order for a clot to form called the clotting cascade. There are many steps in this process, and anticoagulants work in a couple of different areas. Coumadin, or warfarin, is one of the most commonly used anticoagulants. It blocks the effects of vitamin K in the clotting cascade, preventing the activation of clotting factors.

Another group of medications, called direct-acting oral anticoagulants (DOACs) works in a different part of the cascade to block thrombin, another clotting factor. Common medications in this group include Eliquis (apixaban), Xarelto (rivaroxaban), Pradaxa (dabigatran), and Savaysa (edoxaban). In short, these medications work in different parts of the clotting chain in order to prevent clots from forming.

Risks of Anticoagulants

The biggest risk of being on any anticoagulant is bleeding. Since you are inhibiting the process for clots to form, you are increasing the time it takes for your blood to clot when it needs to. For example, if you are cutting vegetables for dinner and slip and slice your finger, it will likely bleed for longer than for someone who is not on an anticoagulant. Some patients experience spontaneous bleeding such as nosebleeds, bleeding gums, or blood in the urine or stool. Bruising (bleeding under the skin) is also a common side effect of anticoagulant therapy. You should immediately inform you doctor, or other healthcare professional in charge of your anticoagulant therapy, if you experience any bleeding. Any serious bleeding which cannot be stopped requires a trip to the ER. Also, any head injuries while on anticoagulants should be taken seriously. You should report to the ER for a CT scan to ensure there is no internal bleeding present.

Tips for preventing bleeding include:

  • Routine blood tests, especially if you take warfarin
  • Avoid activities that are likely to cause head injury or serious cuts
  • Also limit or avoid alcohol consumption while on an anticoagulant, as alcohol can further thin the blood

If you do experience bleeding, there are a few keys to helping it to stop quicker:

  • Applying pressure to the wound
  • Elevating it above the level of your heart
  • Applying ice to the area

Warfarin: Advantages and Disadvantages

Many patients must weigh the advantages and disadvantages to decide which type of anticoagulant is right for them. Warfarin is often chosen because it is more cost-effective. It has also been used successfully for many years so has lots of data to prove that it works well. This is the only anticoagulant approved for patients with certain conditions such as a mechanical heart valve. It can also be quickly reversed in emergency situations by administering vitamin K in the form of dietary, tablet, or injection. However, warfarin dosing and maintenance can be a bit daunting. Patients respond differently to warfarin based on factors such as genetics, diet, and other medications that they take.

Careful Dosage is Important With Warfarin

Dosing is usually not as straightforward either. While many medications can be taken with the same dose every day and increased or decreased easily, warfarin must be adjusted much more carefully. Patients starting on warfarin therapy will have their blood checked frequently, typically twice a week, until a maintenance dose can be determined. The test performed gives a number called an INR (International Normalized Ratio) that tells how “thin” a patient’s blood is. These checks will become more extended as INR stabilizes. Most patients check their blood on a monthly basis. This can be done with a regular lab draw or a simple finger stick in a clinic. Some patients can even test their INR in their own home and report the result to their managing provider. Doses are typically adjusted by a doctor, nurse, or pharmacist and patients are given instructions on when to follow up. They also should tell their managing provider when they have dietary changes, medication changes, or illness that may impact their results.

Vitamin K

Patients on warfarin also have to pay attention to foods that contain vitamin K, since this is the step of the clotting cascade where warfarin works. I like to tell patients to think of it as a tug-of-war between dietary vitamin K and warfarin. The warfarin is trying to thin your blood, but the more vitamin K you add, the more warfarin you will require to overcome it. Common foods that contain vitamin K are green vegetables such as spinach, kale, broccoli, and Brussels sprouts. Patients may eat these foods, but should consume them consistently. Diet is perhaps the most challenging part of warfarin therapy for most patients. If you are a patient on warfarin who is struggling to control your INRs, ask your doctor about enrolling in an anticoagulation clinic. These specialists focus on warfarin therapy and are the experts in regulating your dose. If you are a current CHI Health patient, you can ask to be referred to the Pharmacy Anticoagulation Clinic.

DOAC Therapy: Advantages and Disadvantages

On the other hand, DOACs are much more straightforward. Dosing is relatively simple, and patients take the same dose every day. Frequent blood tests are not required for DOAC therapy. These patients also do not need to watch their vitamin K intake. However, these medications can be cost prohibitive for many patients. While reversal agents are available for DOACs, they are not as easy or readily available either. A patient on warfarin whose blood gets a little too thin can enjoy a spinach salad to help reverse it. This does not work for DOACs since they have no impact on the vitamin K step in the clotting cascade.

In an emergency situation, often the best option for these patients is a blood transfusion. So patients who are opposed to this, such as for religious reasons, are likely better candidates for warfarin therapy.

While anticoagulants may seem scary or overwhelming, they play a very important role in preventing serious clotting incidents. They can be used safely and effectively if taken appropriately and monitored. If you have further questions, talk to your doctor or pharmacist.

Mary Crumley, PharmD

Mary is a clinical pharmacist and supervisor of the CHI Health Pharmacy Anticoagulation Clinic. She is passionate about caring for her patients and loves building relationships with them. In her free time, she enjoys reading, travelling, and spending time with her family.

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