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Reviewed by: HU Medical Review Board | Last reviewed: June 2023

When a person has lupus, their immune system attacks their own body by mistake. Normally, the body responds to infection and other foreign invaders by making antibodies. Antibodies are proteins that target specific threats to the body, but they can start attacking normal, healthy tissues instead. This is what makes conditions like lupus autoimmune conditions.

About one-third to half of all people with lupus will make a specific autoantibody to phospholipid-binding proteins. These proteins normally play a role in the blood clotting process. When antibodies are made against them (called antiphospholipid antibodies), blood clotting can occur. Blood clotting is important in preventing excessive bleeding, however, in some situations, blood clots can be life-threatening. They can increase the risk of stroke, deep vein thrombosis, heart attack, miscarriages, pulmonary embolism (a blood clot in the lung), and even death. When a person has multiple blood clots caused by antiphospholipid antibodies, they are said to have antiphospholipid syndrome (APS).

How do anticoagulants work?

Since blood clots can be common in people with lupus, and some can be serious, blood clot prevention can become an important aspect of lupus care. Drugs called anticoagulants, or blood thinners, can be used to “thin” the blood and reduce the risk that it might clot.

Overall, there is a complex pathway of many different proteins and signaling molecules that allow the blood to clot when needed (like when we get a cut and start bleeding). Each type of anticoagulant impacts a different step or player in this pathway. For example, the anticoagulant warfarin affects the production of vitamin K, which helps the blood clot. With lower levels of vitamin K, the blood doesn’t clot as easily.

Types of anticoagulants

There are many different anticoagulant drugs on the market currently. Common anticoagulants include, but are not limited to:

  • Warfarin (Coumadin)
  • Heparin
  • Dalteparin (Fragmin)
  • Tinzaparin (Innohep)
  • Fondaparinux (Arixtra)
  • Enoxaparin (Lovenox)
  • Rivaroxaban (Xarelto)
  • Dabigatran (Pradaxa)
  • Apixaban (Eliquis)
  • Edoxaban (Savayasa)

What are the possible side effects of anticoagulants?

Because they can thin the blood, serious side effects of anticoagulants include bleeding and gangrene (skin blackening and death of tissue). Rarely, bleeding can be severe and can be associated with specific organs. Bleeding in the kidneys may lead to blood in the urine or back pain, while a stomach bleed may lead to vomiting blood, weakness, black stools, or fainting.

Bleeding can also be in the brain and joints. While these side effects are severe and could be life-threatening, they are rare. In many cases, the risk of not taking a blood thinner and developing a serious blood clot outweighs the risk of experiencing side effects from treatment.

Other side effects of anticoagulants include, but are not limited to:

  • Bloating
  • Diarrhea
  • Bruising
  • Rash
  • Hair loss
  • Pain in toes
  • Itchy feet
  • Yellowing of the eyes or skin (jaundice)
  • Injection site redness, pain, or warmth (if taking an injected drug like heparin)

Your doctor will discuss the risks and benefits of starting an anticoagulant drug before determining if they’re right for you. If you notice signs of excessive bleeding, such as bleeding gums, heavy menstrual bleeding, excessive bruising, nosebleeds, and bleeding for a long time after getting a cut, contact your doctor as soon as possible.

These are not all the possible side effects of anticoagulants. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with anticoagulants.

What to know about anticoagulants

Each anticoagulant can have different properties, doses, warnings, and methods of administration. For example, heparin is given as an injection, while others, like warfarin or dabigatran are taken orally.

Anticoagulants can affect people in different ways

Some anticoagulants, like warfarin, can impact people in different ways, leading to fluctuations in the amount of thinning they cause. Because of this, people taking warfarin require regular blood tests to make sure the blood hasn’t been “thinned” too much. Several of these tests include INR (International Normalized Ratio), and PT (Prothrombin Time).

Some anticoagulants are dangerous during pregnancy

Warfarin also causes severe birth defects and should not be taken by women who are pregnant or planning to become pregnant. Pregnant women may be able to take heparin, however, after pregnancy, they may be switched to a different anticoagulant since long-term heparin may reduce bone density (osteoporosis).

Lifestyle and medication changes should be monitored

People taking an anticoagulant drug should avoid smoking or drinking alcohol as much as possible. These can increase the risk of cardiovascular disease and clotting. Alcohol may also cause stomach irritation and bleeding, as well as interfere with how well anticoagulants work. People taking an anticoagulant may need to avoid certain medications or supplements that can impact how their anticoagulant drug works. These include aspirin, NSAIDs, vitamin K supplements, and fish oil, among others. Some anticoagulants may require special dietary changes. Before starting a new anticoagulant, tell your doctor about any other medications, vitamins, or supplements you take, as well as any other medical conditions you have.

Special tests may be necessary

Your doctor can help you determine any specific risks, testing requirements, and considerations that need to be taken based on the anticoagulant prescribed for you. People taking an anticoagulant should not stop or change their dosage without first talking to their doctor.

Additional treatment options

In addition to anticoagulants, there are other medications people with lupus may be able to use to reduce clotting. These include Plaquenil (hydroxychloroquine) and Rituxan (rituximab). Other lupus-related treatment options outside of those used specifically for clotting include, but are not limited to, NSAIDs, corticosteroids, immunosuppressants, and biologic drugs.1-3

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