Description and Brand Names
US Brand Name
Descriptions
Warfarin is used to prevent or treat blood clots, including deep venous thrombosis or pulmonary embolism. It is also used for blood clots that may be caused by certain heart conditions, open-heart surgery, or after a heart attack. Warfarin is an anticoagulant (blood thinner) that decreases the clotting ability of the blood.
This medicine is available only with your doctor’s prescription.
This product is available in the following dosage forms:
Before Using
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:
Allergies
Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Pediatric
Appropriate studies have not been performed on the relationship of age to the effects of warfarin in the pediatric population. Safety and efficacy have not been established.
Geriatric
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of warfarin in the elderly. However, elderly patients may require caution and an adjustment in the dose, especially those who are at risk of bleeding.
Breastfeeding
Studies in women suggest that this medication poses minimal risk to the infant when used during breastfeeding.
Drug Interactions
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
Defibrotide
Tamoxifen
Viloxazine
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Abametapir
Abciximab
Aceclofenac
Acemetacin
Acenocoumarol
Adagrasib
Adalimumab
Alefacept
Alipogene Tiparvovec
Allopurinol
Alpelisib
Alteplase, Recombinant
Amiodarone
Amoxicillin
Ampicillin
Amtolmetin Guacil
Anagrelide
Anistreplase
Apalutamide
Apixaban
Asciminib
Aspirin
Atazanavir
Azithromycin
Bemiparin
Betrixaban
Bicalutamide
Bimekizumab-bkzx
Bivalirudin
Bromfenac
Bufexamac
Cabozantinib
Cangrelor
Cannabidiol
Cannabis
Capecitabine
Caplacizumab-yhdp
Capmatinib
Carbenicillin
Carboplatin
Cefadroxil
Cefdinir
Cefepime
Cefixime
Cefotaxime
Cefpodoxime
Ceftaroline Fosamil
Ceftazidime
Ceftibuten
Ceftizoxime
Ceftriaxone
Celecoxib
Cephalexin
Cephalothin
Cephapirin
Cephradine
Ceritinib
Chamomile
Choline Salicylate
Cilostazol
Ciprofibrate
Ciprofloxacin
Citalopram
Clarithromycin
Clonixin
Clopidogrel
Cloxacillin
Cobicistat
Collagenase, Clostridium histolyticum
Curcumin
Cyclophosphamide
Dabigatran Etexilate
Dabrafenib
Daclatasvir
Dalteparin
Danaparoid
Dapsone
Darunavir
Dasabuvir
Deferasirox
Desvenlafaxine
Dexibuprofen
Dexketoprofen
Diclofenac
Dicloxacillin
Diflunisal
Dihydroartemisinin
Dipyridamole
Dipyrone
Doxifluridine
Doxorubicin
Doxorubicin Hydrochloride Liposome
Dronedarone
Drotrecogin Alfa
Droxicam
Duloxetine
Econazole
Edoxaban
Efavirenz
Elbasvir
Elvitegravir
Enasidenib
Enoxacin
Enoxaparin
Entacapone
Enzalutamide
Epoprostenol
Eptifibatide
Erlotinib
Erythromycin
Escitalopram
Etodolac
Etofenamate
Etoposide
Etoricoxib
Etravirine
Felbinac
Fenofibrate
Fenofibric Acid
Fenoprofen
Fepradinol
Feprazone
Fish Oil
Floctafenine
Fluconazole
Flufenamic Acid
Fluorouracil
Fluoxetine
Flurbiprofen
Fluvoxamine
Fondaparinux
Fosnetupitant
Garlic
Gatifloxacin
Gemcitabine
Gemfibrozil
Gemifloxacin
Ginkgo
Glucagon
Grazoprevir
Ibrutinib
Ibuprofen
Iloprost
Imatinib
Indomethacin
Infliximab
Influenza Virus Vaccine
Inotersen
Itraconazole
Ivacaftor
Ivosidenib
Ketoconazole
Ketoprofen
Ketorolac
Ledipasvir
Leflunomide
Leniolisib
Lepirudin
Letermovir
Levocarnitine
Levofloxacin
Levomilnacipran
Linezolid
Lomitapide
Lornoxicam
Lovastatin
Loxoprofen
Lumiracoxib
Lycium
Mavacamten
Mechlorethamine
Meclofenamate
Mefenamic Acid
Megestrol
Meloxicam
Melphalan
Mercaptopurine
Methicillin
Methotrexate
Methylphenidate
Methyl Salicylate
Metronidazole
Miconazole
Milk Thistle
Milnacipran
Mirtazapine
Mitotane
Morniflumate
Moxalactam
Moxifloxacin
Nabumetone
Nadroparin
Nafcillin
Nalidixic Acid
Nandrolone
Naproxen
Nepafenac
Netupitant
Niflumic Acid
Nilotinib
Nimesulide
Nimesulide Beta Cyclodextrin
Nintedanib
Nitisinone
Norfloxacin
Noscapine
Obeticholic Acid
Ofloxacin
Omadacycline
Ombitasvir
Omeprazole
Oritavancin
Orlistat
Oseltamivir
Oxacillin
Oxaliplatin
Oxandrolone
Oxaprozin
Oxyphenbutazone
Oxypurinol
Papaya
Parecoxib
Paritaprevir
Paroxetine
Peginterferon Alfa-2b
Penicillin G
Penicillin V
Pentosan Polysulfate Sodium
Phenindione
Phenobarbital
Phenprocoumon
Phenylbutazone
Piketoprofen
Piperacillin
Piracetam
Piroxicam
Pixantrone
Posaconazole
Pranoprofen
Prasugrel
Primidone
Procarbazine
Proglumetacin
Proguanil
Propyphenazone
Proquazone
Regorafenib
Remdesivir
Reteplase, Recombinant
Ribavirin
Rivaroxaban
Rofecoxib
Ropinirole
Rosuvastatin
Roxithromycin
Rucaparib
Sarecycline
Secnidazole
Selexipag
Selumetinib
Sertraline
Simeprevir
Simvastatin
Sitaxsentan
Sofosbuvir
Sparsentan
St John’s Wort
Streptokinase
Sulfamethoxazole
Sulfisoxazole
Sulindac
Sultamicillin
Tan-Shen
Taurursodiol
Tegafur
Telithromycin
Tenecteplase
Tenoxicam
Teriflunomide
Testosterone
Tiaprofenic Acid
Ticagrelor
Ticarcillin
Ticlopidine
Tinzaparin
Tirofiban
Tirzepatide
Tocilizumab
Tocophersolan
Tolfenamic Acid
Tolmetin
Torsemide
Tramadol
Trazodone
Treprostinil
Turmeric
Urokinase
Ustekinumab
Valdecoxib
Valproic Acid
Velpatasvir
Venlafaxine
Vilazodone
Vincristine
Vincristine Sulfate Liposome
Vindesine
Vorapaxar
Voriconazole
Vortioxetine
Voxilaprevir
Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Acarbose
Acetaminophen
Aminoglutethimide
Amitriptyline
Amprenavir
Apazone
Aprepitant
Argatroban
Atovaquone
Azathioprine
Balsalazide
Bee Pollen
Benorilate
Benzbromarone
Bosentan
Butabarbital
Butalbital
Carbamazepine
Carbimazole
Cefamandole
Cefazolin
Chitosan
Chloral Hydrate
Chlorthalidone
Cholestyramine
Choline Magnesium Trisalicylate
Chondroitin
Cimetidine
Cisapride
Cisplatin
Coenzyme Q10
Colesevelam
Cyclosporine
Danazol
Desogestrel
Dexamethasone
Dexlansoprazole
Dienogest
Disopyramide
Disulfiram
Dong Quai
Doxepin
Drospirenone
Eslicarbazepine Acetate
Esomeprazole
Estradiol
Eterobarb
Ethinyl Estradiol
Ethynodiol
Exenatide
Felbamate
Fluoxymesterone
Fluvastatin
Fosaprepitant
Gefitinib
Gestodene
Ginger
Ginseng
Glucosamine
Glyburide
Griseofulvin
Heparin
Ifosfamide
Indoprofen
Isoniazid
Isoxicam
Ivermectin
Lactulose
Lansoprazole
Levamisole
Levonorgestrel
Lopinavir
Melatonin
Menatetrenone
Menthol
Mephobarbital
Mesalamine
Mesna
Mestranol
Methimazole
Methylprednisolone
Methyltestosterone
Methylthiouracil
Moricizine
Nelfinavir
Nevirapine
Niacin
Nilutamide
Nirmatrelvir
Nomegestrol
Norethindrone
Norgestimate
Norgestrel
Pantoprazole
Pentoxifylline
Phytonadione
Polyacrylamide
Potassium Iodide
Prednisone
Propafenone
Propoxyphene
Propylthiouracil
Quetiapine
Ranitidine
Rifabutin
Rifampin
Rifapentine
Ritonavir
Salicylamide
Salicylic Acid
Salsalate
Saquinavir
Secobarbital
Semaglutide
Sodium Salicylate
Sodium Thiosalicylate
Sorafenib
Stanozolol
Sucralfate
Sulfasalazine
Sulfinpyrazone
Tenidap
Terbinafine
Tigecycline
Tolterodine
Trastuzumab
Trolamine Salicylate
Vancomycin
Venetoclax
Vitamin A
Vitamin E
Vorinostat
Zafirlukast
Zileuton
Other Interactions
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following is usually not recommended, but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco.
Cranberry Juice
Pomegranate
Tobacco
Using this medicine with any of the following may cause an increased risk of certain side effects but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco.
Avocado
Black Tea
Enteral Nutrition
Green Tea
High Protein Food
Noni Juice
Soybean
Vitamin K Containing Food
Other Medical Problems
The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:
Anemia or
Catheter insertion or
Congestive heart failure or
Deep venous thrombosis, heparin-induced or
Diabetes or
Falls or blows to the body or head or
Hypertension (high blood pressure) or
Infection or
Kidney disease, or history of or
Major surgery, any type or
Polycythemia vera (blood disease) or
Protein C deficiency (rare hereditary disease), known or suspected or
Stomach or bowel problems, including bleeding or
Thrombocytopenia, heparin-induced or
Trauma or
Vasculitis (inflammation of blood vessel)—Use with caution. May cause side effects to become worse.
Blood disease or bleeding problems or
Heart infection or
High blood pressure (high blood pressure), severe or
Spinal anesthesia, recent or
Stomach or intestinal ulcer, active or
Stroke, history of or
Surgery, recent or scheduled (eg, surgery of the eye, brain, or spine) or
Threatened miscarriage—Should not be used in patients with these conditions. The risk of bleeding from warfarin may be increased.
Diarrhea or
Liver disease or
Malnutrition or
Steatorrhea (fats in the stool) or
Vitamin K deficiency—Use with caution. May increase risk of bleeding.
Proper Use
Take this medicine only as directed by your doctor. Your dose may need to be changed several times in order to find out what works best for you. Do not use more of it, do not use it more often, and do not use it for a longer time than your doctor ordered.
This medicine should come with a Medication Guide. Read and follow these instructions carefully. Ask your doctor if you have any questions.
Carefully follow your doctor’s instructions about any special diet. This medicine works best when you eat about the same amount of vitamin K in your food every day. Tell your doctor before changing your diet. Avoid big changes in how much vitamin K you eat. Some foods that have a high amount of vitamin K are asparagus, broccoli, brussels sprouts, cabbage, green leafy vegetables (such as collards, turnip greens, mustard greens, spinach, and salad greens), plums, rhubarb, and certain vegetable oils (such as soybean oil and canola oil).
You may take the tablets on a full or empty stomach.
Do not drink grapefruit juice while you are using this medicine. Grapefruit juice may change the amount of this medicine that is absorbed in the body.
Dosing
The dose of this medicine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For oral dosage form (tablets):
- For prevention or treatment of blood clots:
- Adult—At first, 2 to 5 milligrams (mg) as a single dose once per day. Your doctor may adjust your dose if needed. However, the dose is usually not more than 10 mg per day.
- Children—Use and dose must be determined by your doctor.
Missed Dose
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Storage
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Precautions
It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood tests, such as an INR, are needed to check for proper dosage and unwanted side effects. Be sure to keep all appointments.
Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant during treatment and for at least 1 month after the last dose. If you think you have become pregnant while using this medicine, tell your doctor right away.
Make sure any doctor or dentist who treats you knows that you are using this medicine. You may need to stop using this medicine several days before having surgery or medical tests.
Check with your doctor immediately if you have diarrhea, fever, or any symptoms of an infection.
This medicine may cause skin necrosis or gangrene. Call your doctor right away if you have pain, a color change, or a temperature change to any area of your body. Call your doctor right away if you have pain in your toes and they look purple or dark in color. These could be signs of a serious medical problem.
Calciphylaxis or calcium uremic arteriolopathy may occur in patients with or without end-stage kidney disease. Tell your doctor right away if you have purplish red, net-like, blotchy spots on the skin.
Warfarin may increase your risk of having kidney problems, including acute kidney injury. Check with your doctor right away if you have blood in the urine, decreased urine output, muscle twitching, nausea, rapid weight gain, seizures, stupor, swelling of the face, ankles, or hands, or unusual tiredness or weakness.
This medicine may increase your chance of bleeding. Check with your doctor right away if you notice any unusual bleeding or bruising, black, tarry stools, blood in the urine or stools, or pinpoint red spots on your skin. Avoid picking your nose. If you need to blow your nose, blow it gently.
Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
Be careful not to cut yourself when you are using sharp objects, such as a safety razor or fingernail or toenail cutters. Avoid contact sports or other situations where bruising or injury could occur.
It is recommended that you carry identification that says you are using warfarin. If you have any questions about what kind of identification to carry, check with your doctor.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription medicines, nonprescription (over-the-counter [OTC]) medicines, and herbal or vitamin supplements.
Side Effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
Less common
- Bleeding gums
- blood in the urine
- bloody stools
- blurred vision
- burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings
- chest pain or discomfort
- confusion
- coughing up blood
- difficulty with breathing or swallowing
- dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
- excessive bruising
- headache
- increased menstrual flow or vaginal bleeding
- nosebleeds
- paralysis
- peeling of the skin
- prolonged bleeding from cuts
- red or black, tarry stools
- red or dark brown urine
- stomach pain with cramping
- sweating
- unexplained swelling
- unusual tiredness or weakness
Rare
- Arm, back, or jaw pain
- blue-green to black skin discoloration
- blue or purple toes
- change in consciousness
- chest tightness or heaviness
- chills
- clay-colored stools
- diarrhea
- dizziness
- fainting or loss of consciousness
- fast or irregular breathing
- fast or irregular heartbeat
- fever
- itching or skin rash
- light-colored stools
- loss of appetite
- nausea and vomiting
- pain in the toes
- pain, redness, or sloughing of the skin
- pale skin
- purplish red, net-like, blotchy spots on the skin
- skin blisters
- small red or purple spots on the skin
- stomach pain
- swelling of the eyes or eyelids
- troubled breathing with exertion
- unpleasant breath odor
- unusual bleeding or bruising
- upper right stomach pain
- vomiting of blood
- yellow eyes and skin
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Less common
Rare
- Bloated
- change in taste, or bad, unusual, or unpleasant (after) taste
- cold intolerance
- excess air or gas in the stomach or intestines
- full feeling
- general feeling of discomfort or illness
- hair loss or thinning of the hair
- hives or welts
- lack or loss of strength
- pain
- passing gas
- red, sore, or itching skin
- sores, welting, or blisters
- unusual drowsiness, dullness, or feeling of sluggishness
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
