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Warfarin

Pronunciation

Generic Name: warfarin (WAR-far-in)
Brand Name: Coumadin

Warfarin can cause severe and sometimes fatal bleeding. Bleeding is more likely to occur at the start of treatment or with high doses. Patients who have a history of stomach or bowel bleeding, high blood pressure, stroke or "mini-stroke" (transient ischemic attack [TIA]), serious heart disease, anemia, cancer, certain genetic factors, or kidney problems may be at greater risk for bleeding. Patients who have inconsistent international normalized ratios (INRs; a blood test), who have taken warfarin for a long time, who have had a recent injury or surgery, or who are 65 years old or older are also at greater risk.

Certain blood clotting tests (eg, prothrombin time [PT], INR) will be performed regularly while you take warfarin. Certain medicines, dietary changes, and other factors may affect INR levels while taking warfarin. Discuss any questions or concerns with your doctor.

Contact your doctor right away if you notice any unusual bleeding or bruising. Symptoms of bleeding problems include unusual bruising; bleeding gums; bloody or coffee ground-like vomit; coughing up blood; dizziness; increased bleeding from cuts; increased menstrual or vaginal bleeding; nosebleeds; pain, swelling, or discomfort; pink or brown urine; red or black stools; unusual headaches or weakness.


Warfarin is used for:

Treating and preventing harmful clots that may occur in the veins (venous thrombosis), in the lungs (pulmonary embolism), with a type of abnormal heartbeat (atrial fibrillation), or following a heart valve replacement. Warfarin is also used to reduce the risk of stroke and other problems in patients who have had a heart attack. It may also be used for other conditions as determined by your doctor.

Warfarin is an anticoagulant. It works by blocking the formation of certain blood clotting factors.

Do NOT use warfarin if:

  • you are allergic to any ingredient in warfarin
  • you have bleeding tendencies, bleeding problems (eg, hemophilia), severe or uncontrolled high blood pressure, certain blood problems (eg, low white blood cell or platelet levels), or leukemia
  • you have active serious bleeding, bleeding in the brain, certain blood vessel problems (eg, aneurysm, dissecting aorta), or inflammation or infection of the heart
  • you have active ulcer or bleeding of the stomach or bowel, urinary tract, genitals, or respiratory tract
  • you have recently had or will be having eye, brain, or spinal cord surgery; spinal puncture; spinal anesthesia; or any type of major surgery
  • you are pregnant, unless you have a mechanical heart valve
  • you are unable to have routine blood clotting tests
  • you are unable to follow your doctor's instructions properly and do not have someone to help you take your medicine
  • you are taking mifepristone, streptokinase, or urokinase

Contact your doctor or health care provider right away if any of these apply to you.

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Before using warfarin:

Some medical conditions may interact with warfarin. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

  • if you are pregnant, planning to become pregnant, or are breast-feeding
  • if you are able to become pregnant
  • if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
  • if you have allergies to medicines or other substances
  • if you have recently been injured, fallen, given birth, or had surgery
  • if you have a history of stomach or bowel problems (eg, bleeding, ulcer, inflammation), heart problems (eg, heart failure, infection), blood clots, anemia or other blood problems (eg, protein C deficiency, high red blood cell levels), blood vessel problems, or high blood pressure
  • if you have a history of liver, kidney, or thyroid problems; yellowing of the skin or eyes; mental or mood problems; high cholesterol; arthritis; diabetes; or cancer
  • if you smoke or drink alcohol, or if you have poor nutrition, celiac disease, nutrient or fat absorption problems, or low levels of vitamin K or vitamin C in the blood
  • if you have a fever, very poor health, diarrhea, fluid buildup, excessive fat in the stools (steatorrhea), a recent or current infection, or tuberculosis (TB), or if you will be exposed to high temperatures for a prolonged period of time
  • if you have a heart valve replacement, an intrauterine device (IUD), or a catheter
  • if you fall often, or if you plan to have any surgery or dental procedure

Some MEDICINES MAY INTERACT with warfarin. Tell your health care provider if you are taking any other medicines, especially any of the following:

  • Antiplatelet medicines (eg, clopidogrel), heparin or other anticoagulants, nonsteroidal anti-inflammatory drugs (NSAIDs) (eg, ibuprofen), salicylates (eg, aspirin), streptokinase, or urokinase because the risk of bleeding may be increased
  • Mifepristone because excessive bleeding may occur
  • Topical pain medicines (medicines applied to your skin) because some of these medicines may increase your risk of bleeding
  • Many prescription and nonprescription medicines (eg, used for allergic reactions, asthma, anxiety, gout, heartburn or reflux, HIV, infections, inflammation, aches and pains, heart problems, high blood pressure, high cholesterol, seizures, trouble sleeping, mental or mood problems, diabetes, stomach or bowel problems, irregular heartbeat, birth control, hormone replacement, cancer, immune system suppression, pulmonary arterial hypertension [PAH], and others), multivitamin products, and herbal or dietary supplements (eg, herbal teas, coenzyme Q10, garlic, ginseng, ginkgo, St. John's wort) may interact with warfarin, increasing the risk of serious side effects such as bleeding or blood clots

This may not be a complete list of all interactions that may occur. Ask your health care provider if warfarin may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use warfarin:

Use warfarin as directed by your doctor. Check the label on the medicine for exact dosing instructions.

  • Warfarin is usually given as an injection at your doctor's office, hospital, or clinic.
  • Do not use warfarin if it contains particles, is cloudy or discolored, or if the vial is cracked or damaged.
  • Keep this product, as well as syringes and needles, out of the reach of children and pets. Do not reuse needles, syringes, or other materials. Ask your health care provider how to dispose of these materials after use. Follow all local rules for disposal.
  • It is very important to take warfarin on a regular schedule as prescribed by your doctor. Take warfarin at the same time each day.
  • Continue to take warfarin even if you feel well. Do not miss any doses, unless directed to do so by your doctor.
  • If you miss a dose of warfarin, contact your doctor right away.

Ask your health care provider any questions you may have about how to use warfarin.

Important safety information:

  • Tell your doctor or dentist that you take warfarin before you receive any medical or dental care, emergency care, or surgery.
  • Carry an ID card at all times that says you take warfarin.
  • Do NOT take more than the recommended dose or use for longer than prescribed without checking with your doctor. Contact your doctor right away if you may have taken too much of warfarin.
  • Do not drink alcohol while you are taking warfarin; it may increase the risk of warfarin's side effects.
  • Do not change your activity level or weight without checking with your doctor; the risk of warfarin's side effects may be increased. Do not participate in any sport or other activity that may cause a serious injury while taking warfarin.
  • Do not change your eating habits without checking with your doctor. Eat a normal, balanced diet. Foods that have high levels of vitamin K (eg, green leafy vegetables, broccoli, liver, certain vegetable oils) may change the effect of warfarin. Ask your doctor for a list of foods that may affect warfarin. Tell your doctor if any foods on the list are a part of your diet.
  • Check with your doctor before you eat cranberries or grapefruit, or before you eat or drink products that contain cranberry or grapefruit while you are taking warfarin. Tell your doctor if these products are already part of your diet.
  • Elevated body temperature may increase the effect of warfarin. Be careful to avoid becoming overheated, especially during hot weather.
  • Warfarin decreases blood clotting. Use caution while doing activities such as brushing your teeth, flossing, or shaving. Avoid activities that may cause bruising or injury. Seek immediate medical attention if you fall or injure yourself. Tell your doctor if you have unusual bruising or bleeding. Tell your doctor if you have dark, tarry, or bloody stools.
  • Tell your doctor if you develop a fever, infection, or severe diarrhea.
  • Do not take aspirin while you take warfarin unless your doctor tells you to. If you already take aspirin for a heart or other condition, talk with your doctor about whether or not you should continue to take it with warfarin.
  • Tell your doctor if you will be traveling or if you will be confined to a bed or chair for a long period of time (eg, car or airplane ride). This may increase your risk of developing a blood clot.
  • If therapy with warfarin is stopped, the blood thinning effects may last for 2 to 5 days after you stop taking it. Discuss any questions or concerns with your doctor. Do not suddenly stop taking warfarin without checking with your doctor.
  • Lab tests, including certain blood clotting tests (eg, PT, INR), may be performed while you use warfarin. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
  • Use warfarin with caution in Asian patients; they may be more sensitive to its effects, especially bleeding.
  • Use warfarin with caution in the ELDERLY; they may be more sensitive to its effects, especially bleeding.
  • Warfarin should be used with extreme caution in CHILDREN; safety and effectiveness in children have not been confirmed. Children may need more frequent lab tests if they use warfarin.
  • If you may become pregnant, you must use an effective form of birth control while you take warfarin. If you have questions about effective birth control, talk with your doctor.
  • PREGNANCY and BREAST-FEEDING: Do not use warfarin if you are pregnant. It has been shown to cause harm to the fetus. Avoid becoming pregnant while you are taking it. If you think you may be pregnant, contact your doctor right away. It is not known if warfarin is found in breast milk. If you are or will be breast-feeding while you use warfarin, check with your doctor. Discuss any possible risks to your baby.

Possible side effects of warfarin:

All medicines may cause side effects, but many people have no, or minor, side effects. No COMMON side effects have been reported with warfarin. Seek medical attention right away if any of these SEVERE side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); back, side, muscle, joint, or stomach pain; black, tarry, or bloody stools; blood in the urine (pink or brown urine); bloody or coffee ground-like vomit; chest pain; decreased urination; dizziness; fainting; fever; numbness or tingling; pain, unusual color, or temperature change in any area of the body; pale skin; purple, dark, or painful toes; shortness of breath; skin sores or ulcers; stroke symptoms (eg, confusion, slurred speech, vision problems, one-sided weakness); sudden, severe pain in your legs, feet, or toes; trouble swallowing; unexplained swelling; unusual bruising or bleeding (eg, nosebleed, unusual bleeding from gums, increased bleeding from cuts, increased menstrual or vaginal bleeding, coughing up blood, bleeding at the injection site); unusual headache or weakness; unusual pain, swelling, or discomfort; wounds or sores that do not heal properly; yellowing of the skin or eyes.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

If OVERDOSE is suspected:

Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center, or emergency room immediately. Symptoms may include black, tarry stools; blood in stools or urine; increased menstrual bleeding; unusual bruising or bleeding.

Proper storage of warfarin:

Warfarin is usually handled and stored by a health care provider. If you are using warfarin at home, store warfarin as directed by your pharmacist or health care provider. Keep warfarin out of the reach of children and away from pets.

General information:

  • If you have any questions about warfarin, please talk with your doctor, pharmacist, or other health care provider.
  • Warfarin is to be used only by the patient for whom it is prescribed. Do not share it with other people.
  • If your symptoms do not improve or if they become worse, check with your doctor.
  • Check with your pharmacist about how to dispose of unused medicine.

This information should not be used to decide whether or not to take warfarin or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about warfarin. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to warfarin. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using warfarin.

Issue Date: September 3, 2014
Database Edition 14.3.1.003
Copyright © 2014 Wolters Kluwer Health, Inc.

Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using this medicine.

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