Common uses

Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic (replacement or mechanical) heart valves, and people who have suffered a heart attack. Warfarin is also used to treat or prevent venous thrombosis (swelling and blood clot in a vein) and pulmonary embolism (a blood clot in the lung). Warfarin is in a class of medications called anticoagulants ('blood thinners'). It works by decreasing the clotting ability of the blood. This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before using

Before taking warfarin,
• tell your doctor and pharmacist if you are allergic to warfarin or any other medications.
• do not take two or more medications that contain warfarin at the same time. Be sure to check with your doctor or pharmacist if you are uncertain if a medication contains warfarin or warfarin sodium.
• tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take, especially antibiotics; aspirin or aspirin-containing products and other nonsteroidal anti-inflammatory drugs such as ibuprofen (Advil, Motrin) and naproxen (Aleve, Naprosyn); heparin; medications for cancer, cholesterol, colds and allergies, depression, diabetes, digestive problems (including ulcers and heartburn), gout, heart disease, mental illness, pain,seizures, thyroid problems, and tuberculosis; oral contraceptives (birth control pills); streptokinase; ticlopidine; or urokinase. Many other medications may also interact with warfarin, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list. Do not take any new medications or stop taking any medication without talking to your doctor.
• tell your doctor and pharmacist what herbal or botanical products you are taking, especially bromelains, coenzyme Q10 (Ubidecarenone), cranberry products, danshen, dong quai, garlic, Ginkgo biloba, ginseng, and St. John's wort. There are many other herbal or botanical products which might affect your body's response to warfarin. Do not start or stop taking any herbal products without talking to your doctor.
• tell your doctor if you have or have ever had a thyroid condition or diabetes. Also tell your doctor if you have an infection, a gastrointestinal illness such as diarrhea, or sprue (an allergic reaction to protein found in grains that causes diarrhea), or an indwelling catheter (a flexible plastic tube that is placed into the bladder to allow the urine to drain out).
• Tell your doctor if you are pregnant, think you might be pregnant, or plan to become pregnant while taking warfarin. You should not take warfarin if you are pregnant. Talk to your doctor about the use of effective birth control while taking warfarin. If you become pregnant while taking warfarin, call your doctor immediately. Warfarin may harm the fetus.
• tell your doctor if you are breast-feeding.
• if you are having surgery, including dental surgery, or any type of medical or dental procedure, tell the doctor or dentist that you are taking warfarin. Your doctor may tell you to stop taking warfarin before the surgery or procedure or change your dosage of warfarin before the surgery or procedure. Follow your doctor's directions carefully and keep all appointments with the laboratory if your doctor orders blood tests to find the best dose of warfarin for you.
• tell your doctor if you drink or have ever drunk large amounts of alcohol. Your doctor will probably tell you not to take warfarin. Avoid drinking alcohol while you are taking this medication.
• If you are going to receive an immunization, such as a flu shot, or any other injection into a muscle, tell the health care professional that you are taking warfarin.

Directions

Follow the directions for using this medicine provided by your doctor. This medicine is usually taken by mouth with or without food, usually once a day or as directed by your doctor or other healthcare professional. It is very important to take it exactly as prescribed. Do not increase the dose, take it more frequently, or stop using it unless directed by your doctor.
Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day.
Some foods can affect how warfarin works in your blood and may affect your treatment and dose. Cranberry juice or other cranberry products might affect how your warfarin works. Talk with your doctor or pharmacist for more details.
Dosage is based on your medical condition and response to treatment. Your doctor or other healthcare provider will monitor you closely while you are taking this medication. Therefore, laboratory tests will be performed periodically.


Cautions

Warfarin can cause serious, possibly fatal bleeding, which is more likely to occur when patients first start this medication and/or when taking too high of a dose. The risk is greater in patients older than 65 years and in those with major injuries/surgeries, previous stomach/intestinal bleeding, or stroke. Your doctor or other healthcare provider will monitor you closely to decrease your risk. Keep all medical/lab appointments.
Possible side effects

Warfarin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
• gas
• change in the way things taste
• tiredness
• pale skin
• loss of hair
• feeling cold or having chills
If you experience any of the following symptoms, or those listed in the IMPORTANT WARNING section, call your doctor immediately:
• hives
• rash
• itching
• difficulty breathing or swallowing
• swelling of the face, throat, tongue, lips, or eyes
• hoarseness
• chest pain or pressure
• swelling of the hands, feet, ankles, or lower legs
• fever
• infection
• nausea
• vomiting
• diarrhea
• loss of appetite
• pain in the upper right part of the stomach
• yellowing of the skin or eyes
• flu-like symptoms
• joint or muscle pain
• difficultly in moving any part of your body
• feelings of numbness, tingling, pricking, burning, or creeping on the skin
• painful erection of the penis that lasts for hours
You should know that warfarin may cause necrosis or gangrene (death of skin or other body tissues). Call your doctor immediately if you notice a purplish or darkened color to your skin, skin changes, ulcers, or an unusual problem in any area of your skin or body, or if you have a severe pain that occurs suddenly, or color or temperature change in any area of your body. Call your doctor immediately if your toes become painful or become purple or dark in color. You may need medical care right away to prevent amputation (removal) of your affected body part.
Warfarin may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.


If you take too much

Any medication taken in excess can have serious consequences. If you suspect an overdose of seek medical attention immediately.
Symptoms of overdose may include:
• bloody or red, or tarry bowel movements
• spitting or coughing up blood
• heavy bleeding with your menstrual period
• pink, red, or dark brown urine
• coughing up or vomiting material that looks like coffee grounds
• small, flat, round red spots under the skin
• unusual bruising or bleeding
• continued oozing or bleeding from minor cuts

Additional information

Eat a normal, healthy diet with the same amount of foods that contain vitamin K; ask your doctor or pharmacist for a list of foods that contain vitamin K. Be sure to talk to your doctor before you make any changes in your diet or try to gain or lose weight. Do not eat large amounts of leafy, green vegetables or certain vegetable oils, such as soybean or canola, that contain large amounts of vitamin K. Avoid juice or products that contain cranberries. Ask your doctor about eating licorice while taking warfarin.
Tell your doctor if you drink nutritional supplements or receive supplements by a feeding tube.

Drug interactions

Coumadin interacts with many other drugs, and these interactions can be dangerous, even fatal. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor. Keep a list with you of all the medicines you use and show this list to any doctor or other healthcare provider who treats you.
Coumadin can interact with the following herbal (botanical) products:
• bromelains;
• coenzyme Q10;
• danshen;
• dong quai;
• garlic;
• ginkgo biloba;
• ginseng; or
• St. John's wort.
Do not use any of these products without first asking your doctor. Some of these herbal products can cause you to bleed while you are also taking Coumadin.