Warfarin can cause very serious (possibly fatal) bleeding. This is more likely to occur when you first start taking this medication and/or when you are taking too much warfarin.

To decrease your risk for bleeding, your doctor or other health care provider will monitor you closely and check your lab results (INR test) to make sure you are not taking too much warfarin. Keep all medical and laboratory appointments. Tell your doctor immediately if you notice any signs of serious bleeding. See also Side Effects section.

This medication is used to treat blood clots (such as in deep vein thrombosis-DVT or pulmonary embolus-PE) and/or to prevent new clots from forming in your body. Preventing harmful blood clots helps to reduce the risk of a stroke or heart attack. Conditions that increase your risk of developing blood clots include a certain type of irregular heart rhythm (atrial fibrillation), heart valve replacement, recent heart attack, and certain surgeries (such as hip/knee replacement).

Warfarin is commonly called a "blood thinner," but its more correct term is "anticoagulant." It helps to keep blood flowing smoothly in your body by decreasing the amount of certain substances (clotting proteins) in your blood.

Read the Medication Guide provided by your pharmacist before you start taking warfarin and each time you get a refill. If you have any questions, consult your doctor or pharmacist.

Take this medication by mouth with or without food, usually once a day or as directed by your doctor or other health care professional. It is very important to take it exactly as directed. Do not increase the dose, take it more frequently, or stop using it unless directed by your doctor.

Dosage is based on your medical condition, laboratory tests (such as INR), and response to treatment. Your doctor or other health care provider will monitor you closely while you are taking this medication to determine the right dose for you.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day.

It is important to eat a balanced, consistent diet while taking warfarin. Some foods can affect how warfarin works in your body and may affect your treatment and dose. Avoid sudden large increases or decreases in your intake of foods high in vitamin K (such as broccoli, cauliflower, cabbage, Brussels sprouts, kale, spinach, and other green leafy vegetables, liver, green tea, certain vitamin supplements). If you are trying to lose weight, check with your doctor before you try to go on a diet.

Cranberry products may also affect how your warfarin works. Limit the amount of cranberry juice (2 cups/16 ounces a day) or other cranberry products you may drink or eat.

Nausea, loss of appetite, or stomach/abdominal pain may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

This medication can cause serious bleeding if it affects your blood clotting proteins too much (shown by unusually high INR lab results). Even if your doctor stops your medication, this risk of bleeding can continue for up to a week. Tell your doctor immediately if you have any signs of serious bleeding, including: unusual pain/swelling/discomfort, unusual/easy bruising, prolonged bleeding from cuts or gums, persistent/frequent nosebleeds, unusually heavy/prolonged menstrual flow, pink/dark urine, coughing up blood, vomit that is bloody or looks like coffee grounds, severe headache, dizziness/fainting, unusual or persistent tiredness/weakness, bloody/black/tarry stools, chest pain, shortness of breath, difficulty swallowing.

Tell your doctor immediately if any of these unlikely but serious side effects occur: persistent nausea/vomiting, severe stomach/abdominal pain, yellowing eyes/skin.

This drug rarely has caused very serious (possibly fatal) problems if its effects lead to small blood clots (usually at the beginning of treatment). This can lead to severe skin/tissue damage that may require surgery or amputation if left untreated. Patients with certain blood conditions (protein C or S deficiency) may be at greater risk. Seek immediate medical attention if any of these rare but very serious side effects occur: painful/red/purplish patches on the skin (such as on the toe, breast, abdomen), change in the amount of urine, vision changes, confusion, slurred speech, weakness on one side of the body.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking warfarin, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: bleeding disorders (such as hemophilia).

Before using this medication, tell your doctor or pharmacist your medical history, especially of: liver disease, alcohol use/abuse, mental/mood disorders (including memory problems), recent major injury/surgery, bleeding problems (such as bleeding of the stomach/intestines, bleeding in the brain), blood vessel disorders (such as aneurysms), blood disorders (such as anemia, polycythemia), heart failure, thyroid problems, family member who did not respond to warfarin treatment, frequent falls/injuries, vitamin deficiency or absorption problems.

It is important that all your doctors and dentists know that you take warfarin. Before having surgery or any medical/dental procedures, tell your doctor or dentist that you are using this medication.

Avoid getting injections into the muscles. If you must have an injection into a muscle (for example, a flu shot), it should be given in the arm. This way, it will be easier to check for bleeding and/or apply pressure bandages.

This medication may cause stomach bleeding. Daily use of alcohol while using this medicine will increase your risk for stomach bleeding and may also affect how this medication works. Limit or avoid alcoholic beverages.

If you have not been eating well, if you have an illness or infection that causes fever, vomiting, or diarrhea for more than 2 days, or if you start using any antibiotic medications, contact your doctor or pharmacist immediately because these conditions can affect how warfarin works.

This medication can cause heavy bleeding. To lower the chance of getting cut, bruised, or injured, use great caution with sharp objects like safety razors and nail cutters. Use an electric razor when shaving and a soft toothbrush when brushing your teeth. Avoid activities such as contact sports. If you fall or injure yourself, especially if you hit your head, call your doctor immediately. Your doctor may need to check you.

The Food & Drug Administration has stated that generic warfarin products are interchangeable. However, consult your doctor or pharmacist before switching warfarin products. Be careful not to take more than one medication that contains warfarin unless specifically directed by the doctor or health care provider who is monitoring your warfarin treatment.

Older adults may be at greater risk for bleeding while using this drug.

This medication is not recommended for use during pregnancy because of serious (possibly fatal) harm to an unborn baby. Discuss reliable forms of birth control with your doctor. If you become pregnant or think you may be pregnant, tell your doctor immediately. If you are planning pregnancy, discuss a plan for managing your condition with your doctor before you become pregnant. Your doctor may switch the type of medication you use during pregnancy.

This medication does not pass into breast milk. While there have been no reports of harm to nursing infants, consult your doctor before breast-feeding.

Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any drug, vitamin, or herbal product without checking with your doctor or pharmacist first.

Warfarin interacts with many prescription, nonprescription, vitamin, and herbal products. This includes medications that are applied to the skin or inside the vagina or rectum. The following interactions listed do not contain all possible drug interactions. The interactions with warfarin usually result in an increase or decrease in the "blood-thinning" (anticoagulant) effect. Your doctor or other health care professional should closely monitor you to prevent serious bleeding or clotting problems. While taking warfarin, it is very important to tell your doctor or pharmacist of any changes in medications, vitamins, or herbal products that you are taking.

This drug should not be used with the following medications because very serious interactions may occur: imatinib, mifepristone.

If you are currently using any of these medications listed above, tell your doctor or pharmacist before starting warfarin.

Aspirin and aspirin-like drugs (salicylates) and nonsteroidal anti-inflammatory drugs (NSAIDs such as ibuprofen, naproxen, celecoxib) may have effects similar to warfarin. These drugs may increase the risk of bleeding problems if taken during treatment with warfarin. Carefully check all prescription/nonprescription product labels (including drugs applied to the skin such as pain-relieving creams) since the products may contain NSAIDs or salicylates. Talk to your doctor about using a different medication (such as acetaminophen) to treat pain/fever. Low-dose aspirin and related drugs (such as clopidogrel, ticlopidine) should be continued if prescribed by your doctor for specific medical reasons such as heart attack or stroke prevention. Consult your doctor or pharmacist for more details.

Many herbal medications have "blood-thinning" or "blood-clotting" effects, and some may directly affect warfarin. Tell your doctor before taking any herbal products, especially bromelains, coenzyme Q10, cranberry, danshen, dong quai, fenugreek, garlic, ginkgo biloba, ginseng, goldenseal, and St. John's wort, among others.

This medication may interfere with a certain laboratory test to measure theophylline levels, possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US National Poison Hotline at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: bloody/black/tarry stools, pink/dark urine, unusual/prolonged bleeding.

Do not share this medication with others.

Laboratory and/or medical tests (such as INR, complete blood count) must be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

For the best possible benefit, do not miss any doses. If you do miss a dose, take it as soon as you remember if it is on the same day. If it is the next day, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up because this could increase your risk for bleeding. Keep a record of missed doses to give to your doctor or pharmacist. Contact your doctor or pharmacist if you miss 2 or more doses in a row.

Store at room temperature away from light and moisture. Storage temperature ranges differ according to different manufacturers, so consult your pharmacist for more information. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

MEDICAL ALERT: Your condition and medication can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-800-854-1166 (USA) or 1-800-668-1507 (Canada).

Information last revised October 2008 Copyright(c) 2008 First DataBank, Inc.