Patient education: Choosing a medicine for blood clots (The Basics)

What is a blood clot? — Normally, your body is protected from bleeding because your blood vessels seal over after an injury. The seal is made by proteins and cells in the blood. Sometimes, these proteins and cells form a "clot" inside a blood vessel. Blood clots can be dangerous because they can stop blood from flowing. They can also break off and travel in the bloodstream to another part of the body, like the brain or the lungs.

Medicines used for blood clots are also known as "anticoagulants" or "blood thinners." They do not actually thin the blood. They just make the blood less likely to form clots.

There are several medicines that can be used, including many that can be taken as a pill. These include:

●Apixaban (brand name: Eliquis)

●Dabigatran (brand name: Pradaxa)

●Edoxaban (brand names: Savaysa, Lixiana)

●Rivaroxaban (brand name: Xarelto)

●Warfarin (brand name: Jantoven)

Why would I need one of these medicines? — The main reason doctors prescribe these medicines is to prevent blood clots or to treat blood clots that have already formed.

Doctors prescribe these medicines to prevent blood clots in:

●People who have a heart rhythm problem called "atrial fibrillation" – In people with this condition, the medicine helps lower the chances of forming a blood clot in the heart. A blood clot in the heart can travel to the brain and cause a stroke.

●People who have had surgery – The medicine helps prevent a blood clot in the legs (called a "deep vein thrombosis" or "DVT") or the lungs (called a "pulmonary embolism" or "PE"). This is especially important after certain surgeries, like hip or knee replacement, or in people with cancer. But blood clots can happen after many types of surgery.

●People who have a mechanical heart valve – This is a device used to replace a damaged heart valve.

●Other people who are at high risk of having a blood clot.

Nothing can completely prevent all blood clots, but these medicines can make clots less likely to form.

Doctors also prescribe these medicines for people who have already had a clot, to stop it from getting worse. This is called "secondary prevention." This includes:

●People who have had a stroke related to atrial fibrillation

●People who have had a DVT or PE

●People who have had a blood clot in another part of the body

How do these medicines help? — These medicines do not dissolve clots, but they keep them from growing bigger and they prevent new clots from forming. If a clot breaks off and travels to a lung or to the brain, it can cause serious problems.

What are the differences among these medicines? — There are many differences. Some of the more important differences are how often you take the medicine, whether you need to change your diet, which other medicines might affect how it works, and whether you need regular blood tests.

The table answers some common questions about the differences (table 1). Some of the main differences include:

●How often you take the pills – This depends on which medicine you take and why your doctor prescribed it. Warfarin, edoxaban, and rivaroxaban are taken once a day. If you have a blood clot, rivaroxaban is taken twice a day for the first 3 weeks, and some people with heart disease take a low dose of rivaroxaban twice a day. Apixaban and dabigatran are usually taken twice a day. If you are taking the pills to treat a new blood clot, the first week or more of treatment might be different. Your doctor, nurse, or pharmacist will tell you how many times you need to take your medicine each day.

●Whether you need to change your diet – Warfarin blocks vitamin K, so if you take warfarin, it is important to get about the same amount of vitamin K each day. Different foods have different amounts of vitamin K (table 2).

●Whether you need regular blood tests – If you take apixaban, dabigatran, edoxaban, or rivaroxaban, you will not need regular blood tests.

If you take warfarin, you will need to get your blood tested on a regular schedule to check how it is clotting. This is important in order to make sure you are always getting the dose you need.

●The risk of bleeding – Most kinds of bleeding – including bleeding in the brain – are less likely with apixaban, dabigatran, edoxaban, and rivaroxaban than they are with warfarin. But all of these medicines raise your risk of bleeding more than normal. This can be serious internal bleeding, like bleeding in the brain or the intestines, or external bleeding, like after you get a cut.

●What happens if I miss a dose – If you miss a dose of apixaban, dabigatran, edoxaban, or rivaroxaban, you might not be as well protected from blood clots because these medicines leave your system quickly. If you miss a dose of warfarin, it will still work correctly. Ask your doctor or pharmacist what to do if you miss a dose of your medicine.

Which medicine is right for me? — Your doctor can talk to you about your condition, options, and preferences. For some people, warfarin is the best choice. This includes people with a mechanical heart valve or people with a condition called "antiphospholipid syndrome."

For others, one of the other medicines might be a better choice.

These medicines are not recommended during pregnancy. If you get pregnant and need to take a medicine for blood clots, you will need to take a different medicine that comes in a shot. Make sure to tell your doctor if you get pregnant or if you are trying to get pregnant.

For more detailed information about your medicines, ask your doctor or nurse for the patient hand-out from Lexicomp available through UpToDate. It explains how to use each medicine, describes its possible side effects, and lists other medicines or foods that can affect how it works.

More on this topic

Patient education: Taking medicines for blood clots (The Basics)
Patient education: Stroke (The Basics)
Patient education: Deep vein thrombosis (blood clot in the legs) (The Basics)
Patient education: Pulmonary embolism (blood clot in the lungs) (The Basics)
Patient education: Atrial fibrillation (The Basics)
Patient education: Medicines for atrial fibrillation (The Basics)
Patient education: Prosthetic valves (The Basics)
Patient education: Prothrombin time (PT) test and International Normalized Ratio (INR) (The Basics)

Patient education: Warfarin (Beyond the Basics)
Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)
Patient education: Pulmonary embolism (Beyond the Basics)