Generic Name: warfarin (injection) (WAR far in)
Brand Name: Coumadin
What is warfarin?
Warfarin is an anticoagulant (blood thinner). Warfarin reduces the formation of blood clots.
Warfarin is used to treat or prevent blood clots in veins or arteries, which can reduce the risk of stroke, heart attack, or other serious conditions.
Warfarin may also be used for purposes not listed in this medication guide.
What is the most important information I should know about warfarin?
You should not use warfarin if you have a bleeding disorder, a blood cell disorder, blood in your urine or stools, stomach bleeding, very high blood pressure, an infection of the lining of your heart, bleeding in your brain, recent or upcoming surgery, or if you need a spinal tap or epidural. Do not use warfarin if you cannot use it on time every day.
Do not use warfarin if you are pregnant, unless your doctor tells you to.
Warfarin increases your risk of bleeding, which can be severe or life-threatening. You will need frequent tests to measure your blood-clotting time. Call your doctor or seek emergency medical attention if you have bleeding that will not stop, if you have blood in your urine, black or bloody stools, or if you cough up blood or vomit that looks like coffee grounds.
Many drugs can cause serious medical problems when used with warfarin. Tell your doctor about all medicines you have recently used.
What should I discuss with my healthcare provider before using warfarin?
You should not use warfarin if you are allergic to it, or if you have:
hemophilia or any bleeding disorder that is inherited or caused by disease;
a blood cell disorder (such as low red blood cells or low platelets);
blood in your urine or stools, or if you have been coughing up blood;
an infection of the lining of your heart (bacterial endocarditis);
stomach or intestinal bleeding or ulcer;
very high blood pressure;
recent or upcoming surgery on your brain, spine, or eye;
recent head injury, aneurysm, or bleeding in the brain; or
if you undergo a spinal tap or spinal anesthesia (epidural).
You should not use warfarin if you cannot be reliable in using it because of alcoholism, psychiatric problems, dementia, or similar conditions.
Warfarin can make you bleed more easily, especially if you have:
a history of bleeding problems;
high blood pressure or severe heart disease;
kidney or liver disease;
a disease affecting the blood vessels in your brain;
a history of stomach or intestinal bleeding;
a surgery or medical emergency, or if you receive any type of injection (shot);
if you are 65 or older; or
if you are severely ill or debilitated.
Do not use warfarin if you are pregnant, unless your doctor tells you to. Warfarin can cause birth defects, but preventing blood clots may outweigh any risks to the baby. You may be able to use warfarin during pregnancy if you have a mechanical heart valve. Use effective birth control to prevent pregnancy while using warfarin and for at least 1 month after your last dose. Tell your doctor right away if you become pregnant.
To make sure warfarin is safe for you, tell your doctor if you have:
celiac sprue (an intestinal disorder);
congestive heart failure;
a connective tissue disorder such as Marfan Syndrome, Sjögren syndrome, scleroderma, rheumatoid arthritis, or lupus;
a hereditary clotting deficiency (warfarin may make your symptoms worse at first);
if you use a catheter; or
if you have ever had low blood platelets after receiving heparin.
It is not known whether warfarin passes into breast milk. Tell your doctor if you are breast-feeding a baby. Watch for signs of bruising or bleeding in the baby if you use warfarin while you are nursing.
How should I use warfarin?
Use this medicine at the same time every day. Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Never use a double dose, and do not use warfarin for longer than recommended.
Warfarin injection is given through an IV into a vein. You may be shown how to use an IV at home. Do not give yourself this medicine if you do not understand how to use the injection, and how to properly mix and store the medicine.
While using warfarin, you will need frequent "INR" or prothrombin time tests (to measure how long it takes your blood to clot). Your blood work will help your doctor determine the best dose for you. You must remain under the care of a doctor while using warfarin.
If you have received warfarin in a hospital, call or visit your doctor 3 to 7 days after you leave the hospital. Your INR will need to be tested at that time. Do not miss any follow-up appointments.
Tell your doctor if you are sick with diarrhea, fever, chills, or flu symptoms, or if your body weight changes.
You may need to stop using warfarin 5 to 7 days before having any surgery or dental work. Call your doctor for instructions. You may also need to stop using warfarin if you need to take antibiotics, or if you have a spinal tap or spinal anesthesia (epidural).
Wear a medical alert tag or carry an ID card stating that you use warfarin. Any medical care provider who treats you should know that you are using this medicine.
Store this medicine in the original container at room temperature, away from moisture, heat, and light. After mixing your injection, use it within 4 hours. Do not refrigerate.
What happens if I miss a dose?
Use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose can cause excessive bleeding.
What should I avoid while using warfarin?
Avoid activities that may increase your risk of bleeding or injury. Use extra care to prevent bleeding while shaving or brushing your teeth. You may still bleed more easily for several days after you stop using warfarin.
Avoid drinking alcohol.
Grapefruit juice, cranberry juice, noni juice, and pomegranate juice may interact with warfarin and lead to unwanted side effects. Avoid the use of these juice products while using warfarin.
Avoid making any changes in your diet without first talking to your doctor. Foods that are high in vitamin K (liver, leafy green vegetables, or vegetable oils) can make warfarin less effective. If these foods are part of your diet, eat a consistent amount on a weekly basis.
Ask your doctor before taking any medicine for pain, arthritis, fever, or swelling. This includes acetaminophen (Tylenol), aspirin, ibuprofen (Advil, Motrin), naproxen (Aleve), celecoxib (Celebrex), diclofenac, indomethacin, meloxicam, and others. These medicines may affect blood clotting and may also increase your risk of stomach bleeding.
Warfarin side effects
Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Warfarin may cause you to bleed more easily, which can be severe or life-threatening. Seek emergency medical attention if you have any unusual bleeding, or bleeding that will not stop. You may also have bleeding on the inside of your body, such as in your stomach or intestines. Call your doctor at once if you have blood in your urine, black or bloody stools, or if you cough up blood or vomit that looks like coffee grounds.
Also call your doctor at once if you have:
pain, swelling, hot or cold feeling, skin changes, or discoloration anywhere on your body;
sudden and severe leg or foot pain, foot ulcer, purple toes or fingers;
sudden headache, dizziness, or weakness;
easy bruising or bleeding (nosebleeds, bleeding gums), purple or red pinpoint spots under your skin;
bleeding from wounds or needle injections that will not stop;
pale skin, feeling light-headed or short of breath, rapid heart rate, trouble concentrating;
dark urine, jaundice (yellowing of the skin or eyes);
little or no urinating;
numbness or muscle weakness; or
pain in your stomach, back, or sides.
Common side effects may include:
nausea, vomiting, mild stomach pain;
bloating, gas; or
altered sense of taste.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
What other drugs will affect warfarin?
Many drugs (including some over-the-counter medicines and herbal products) can affect your INR and may increase the risk of bleeding if you take them with warfarin. Not all possible drug interactions are listed in this medication guide. It is very important to ask your doctor and pharmacist before you start or stop using any other medicine, especially:
other medicines to prevent blood clots;
medicine to treat any type of infection, including tuberculosis;
supplements that contain vitamin K; or
an antidepressant--citalopram, duloxetine, fluoxetine, fluvoxamine, paroxetine, sertraline, venlafaxine, vilazodone, and others; seizure medicine--carbamazepine, phenobarbital, phenytoin; herbal (botanical) products--coenzyme Q10, cranberry, echinacea, garlic, ginkgo biloba, ginseng, goldenseal, or St. John's wort.
This list is not complete and many other drugs can interact with warfarin. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Give a list of all your medicines to any healthcare provider who treats you.
More about Coumadin (warfarin)
- Side Effects
- During Pregnancy or Breastfeeding
- Dosage Information
- Drug Images
- Drug Interactions
- Support Group
- Pricing & Coupons
- 15 Reviews – Add your own review/rating
- Generic Availability
- Drug class: coumarins and indandiones
Other brands: Jantoven
Related treatment guides
Where can I get more information?
- Your pharmacist can provide more information about warfarin.
- Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
- Disclaimer: Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.
Copyright 1996-2012 Cerner Multum, Inc. Version: 1.02.
Date modified: May 03, 2017
Last reviewed: September 20, 2016