Blood thinners

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Blood thinners decrease the ability of the blood to clot (coagulate). They do not actually thin the blood. Used to treat certain blood vessel and heart and lung conditions, they may prevent existing clots from becoming larger and causing more serious problems, and are often prescribed to prevent a first or recurrent stroke. Also given to certain people at risk for forming blood clots, such as those with artificial heart valves or who have Atrial Fibrillation (AF). Common anticoagulant drugs are heparin and warfarin (Coumadin).

Blood-thinners are usually given by mouth. Bleeding may be a complication of anticoagulants. Tell your doctor if you begin to bruise easily, or you notice unusual bleeding anywhere including gums or nosebleeds.  

Oral Medications

These mainly include aspirin or clopidogrel (Plavix) and warfarin (Coumadin). These medications decrease the clotting tendency by interfering with platelets or blocking the body’s production of clotting substances. New medications have recently come to the market. Dabigatran and Rivaroxaban are  so-called oral “direct thrombin inhibitors” and may provide the first alternative to Coumadin for the treatment of strokes. 

Neither Dabigatran or Rivaroxaban will need the frequent blood checks as we do for Coumadin, which is something that most patients will be excited about. 

Intravenous Medications

Intravenous heparin acts rapidly to thin the blood. When it’s stopped, the effect also wears off rapidly. Oral anticoagulants are longer-acting, so if you need elective surgery (including dental surgery), these medications may need to be stopped and intravenous or subcutaneous, shorter-acting heparin begun in the hospital before surgery, often referred to as “bridging”. 

Subcutaneous Medications

There are two blood-thinning medications: heparin and low-molecular-weight heparin (Lovenox). Both can be injected just underneath the skin (subcutaneously). This is sometimes done if it’s required for a longer time (e.g., during pregnancy) and eliminates the need for an intravenous line long-term. Your cardiologist will determine which type of blood-thinning medication is best for you.  


If you’re taking warfarin, your doctor will regularly monitor the blood-clotting level to be sure your dosage is correct. A value called the INR (international normalized ratio) tests how quickly your blood clots. Your warfarin dosage will be carefully adjusted to maintain an INR level appropriate for your condition. If you need heparin or low-molecular-weight heparin, blood tests are also required to check that the dose is correct. 

Medication and Diet Interactions with Warfarin

Many over-the-counter or prescription medicines can interact with warfarin and change your INR, which can be hazardous. These medicines include most antibiotics, several pain medicines (e.g., non-steroidal anti-inflammatory drugs) and some medications for acid reflux GERD. 

In general, avoid aspirin when you’re being treated with warfarin. If you have a mechanical heart valve, low-dose aspirin may be added to warfarin to help prevent blood clots from forming.

Certain foods also interfere with how your body processes warfarin. Always ask your doctor about your diet and before taking any other medicines, including vitamins and herbal preparations. 

Anticoagulation in Pregnancy

Women who require anticoagulation and become pregnant need to take special precautions. Warfarin (Coumadin) poses significant risk to the fetus, especially in the first trimester. Many women on warfarin are switched to heparin during the first weeks of pregnancy.

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