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Warfarin, Oral WAR-far-in

What are other names for this medicine?

Type of medicine: anticoagulant (medicine that reduces the chance of blood clots forming)

Generic and brand names: warfarin, oral; Coumadin; Jantoven

What is this medicine used for?

This medicine is taken by mouth to reduce the chance of blood clots forming in your body. This medicine may be used for other conditions as determined by your healthcare provider.

What should my healthcare provider know before I take this medicine?

Before taking this medicine, tell your healthcare provider if you have ever had:

  • an allergic reaction to any medicine
  • a stroke
  • bleeding problems
  • cancer
  • dementia
  • diabetes
  • heart disease
  • high blood pressure
  • kidney or liver disease
  • problems with alcohol or drug abuse
  • stomach ulcers
  • thyroid problems

Tell your provider if you have recently had surgery or any kind of infection.

Females of childbearing age: Do not take this medicine if you are pregnant. This medicine has been reported to cause birth defects. Stop taking this medicine at the first sign that you may be pregnant and contact your healthcare provider right away. Do not breast-feed while taking this medicine without your healthcare provider’s approval.

How do I take it?

Check the label on the medicine for directions about your specific dose. Take this medicine exactly as your healthcare provider prescribes. Take this medicine around the same time every day. Do not take less or the medicine may not be effective. Taking more may cause bleeding. Do not stop taking this medicine without your healthcare provider's approval.

Read the Medication Guide that comes in the medicine package when you start taking this medicine and each time you get a refill.

Do not change brands of this medicine without talking to your healthcare provider or pharmacist. Other brands may affect you differently.

What if I miss a dose?

If you miss a dose of this medicine, take it as soon as you remember on the same day. Do not take a double dose. If you miss a day's dose, contact your healthcare provider right away.

What if I overdose?

If you or anyone else has intentionally taken too much of this medicine, call 911 or go to the emergency room right away. If you pass out, have seizures, weakness or confusion, or have trouble breathing, call 911. If you think that you or anyone else may have taken too much of this medicine, call the poison control center. Do this even if there are no signs of discomfort or poisoning. The poison control center number is 800-222-1222.

Symptoms of an acute overdose may include: blood in the urine or stools, vomiting blood, bleeding that won't stop.

What should I watch out for?

You will need to have blood and lab tests regularly to see how this medicine affects you. Keep all appointments for these tests.

This medicine may cause you to bleed more easily or to bleed longer. Avoid sports and activities that may cause injuries. Talk with your healthcare provider about which sports or activities you should avoid. If you fall or are injured, contact your healthcare provider right away. Serious internal bleeding may occur without you being aware of it.

Adults over the age of 65 may be at greater risk for side effects. Talk to your healthcare provider about this.

Many other medicines, even aspirin and vitamins, may affect the action of this medicine. Tell your healthcare provider and pharmacist about any other prescription or nonprescription medicines, vitamins, or natural remedies you are taking. Do not take any other medicines unless your healthcare provider approves. Also, do not stop taking any medicines without talking to your healthcare provider or pharmacist.

Follow the diet and exercise program your healthcare provider recommends. Some foods may affect how this medicine works in your body. Vitamin K may decrease the effect of this medicine. While you are taking this medicine, eat a healthy balanced diet with about the same amount of vitamin K each day. Vitamin K is found in leafy green vegetables, certain legumes, green tea, and vegetable oils. Do not make big changes in your diet, such as eating a lot more green leafy vegetables than you usually eat.

If you need emergency care, surgery, lab tests, or dental work, tell the healthcare provider or dentist you are taking this medicine. Always carry a form of identification stating that you take this medicine, such as a medical alert bracelet or ID card.

Contact your healthcare provider if you have not been eating well for 2 days or if you have an illness or infection that causes fever, diarrhea, or vomiting. These problems may change the effect of this medicine.

Drinking too much alcohol may interfere with this medicine. Talk to your healthcare provider about this.

What are the possible side effects?

Along with its needed effects, your medicine may cause some unwanted side effects. Some side effects may be very serious. Some side effects may go away as your body adjusts to the medicine. Tell your healthcare provider if you have any side effects that continue or get worse.

Life-threatening (Report these to your healthcare provider right away). If you cannot reach your healthcare provider right away, get emergency medical care or call 911 for help): Allergic reaction (hives; itching; rash; trouble breathing; chest pain or tightness in your chest; swelling of your lips, tongue, and throat).

Serious (report these to your healthcare provider right away): Unusual bruising or bleeding; dark urine or stools; bloody urine; increased menstrual flow or vaginal bleeding; discolored fingers or toes; mouth sores; swelling, numbness, or tingling in fingers or toes, or any unexplained swelling; sore throat; fever; yellowish eyes or skin; severe headache, dizziness, or weakness; diarrhea; rash; itching; stomach pain; severe joint or muscle pain; shortness of breath; trouble moving or swallowing.

Other (usually temporary): Bloating, gas, loss of appetite, hair loss.

What products might interact with this medicine?

Do not take any other medicines, including nonprescription products, vitamins, or natural remedies unless your healthcare provider approves. When you take this medicine with other medicines, it can change the way this or any of the other medicines work. Nonprescription medicines, vitamins, natural remedies, and certain foods may also interact. Using these products together might cause harmful side effects, such as bleeding or other serious side effects. Talk to your healthcare provider if you are taking:

  • pain medicine such as acetaminophen (Tylenol), celecoxib (Celebrex), diclofenac (Voltaren, Cataflam), diflunisal, fenoprofen (Nalfon), ibuprofen (Motrin, Motrin IB, Advil), indomethacin (Indocin), ketoprofen, ketorolac (Toradol), mefenamic acid (Ponstel), nabumetone (Relafen), naproxen (Naprosyn, Anaprox, Aleve, Naprelan), oxaprozin (Daypro), piroxicam (Feldene), sulindac (Clinoril), and tramadol (Ultram)
  • antiandrogen medicine such as danazol (Danocrine) and oxymetholone (Anadrol-50)
  • antianxiety medicine such as chlordiazepoxide (Librium)
  • antibiotics such as ampicillin (Omnipen), azithromycin (Zithromax, Z-pak), cefamandole (Mandol), cefazolin (Ancef, Kefzol), cefoperazone (Cefobid), cefotetan, cefoxitin (Mefoxin), ceftriaxone (Rocephin), chloramphenicol, ciprofloxacin (Cipro), clarithromycin (Biaxin), demeclocycline, dicloxacillin (Dycill), doxycycline (Adoxa, Doryx, Monodox, Vibramycin), erythromycin (Ery-Tabs, E.E.S.), griseofulvin (Fulvicin, Grisactin, Gris-Peg), isoniazid, levofloxacin (Levaquin), minocycline (Minocin), nalidixic acid (NegGram), neomycin, norfloxacin (Noroxin), ofloxacin (Floxin), oxacillin (Bactocill), penicillin, piperacillin (Pipracil, Zosyn), rifampin (Rifadin, Rimactane), sulfamethoxazole (Bactrim, Septra), sulfisoxazole (Gantrisin), tetracycline (Achromycin V), and ticarcillin (Ticar, Timentin)
  • antiseizure medicines such as carbamazepine (Tegretol), phenytoin (Dilantin), primidone (Mysoline), and valproic acid (Depacon, Depakene, Depakote)
  • antifungal medicines such as clotrimazole, fluconazole (Diflucan), itraconazole (Sporanox), ketoconazole (Nizoral), metronidazole (Flagyl), and miconazole (Monistat, Micatin)
  • antihistamines such as chlorpheniramine (Chlor-Trimeton) and diphenhydramine (Benadryl)
  • anti-HIV medicines such as indinavir (Crixivan), nelfinavir (Viracept), nevirapine (Viramune), ritonavir (Norvir), and saquinavir (Invirase)
  • antipsychotic medicine such as clozapine (Clozaril) and haloperidol (Haldol)
  • aspirin and other salicylates
  • asthma medicine such as zafirlukast (Accolate) and zileuton (Zyflo)
  • barbiturates such as butabarbital (Butisol), pentobarbital (Nembutal), and phenobarbital
  • birth control pills, patches, and vaginal rings, and hormones such as estradiol (Estrace, Estratab), conjugated estrogens (Premarin), norethindrone (Aygestin, Micronor), and norgestrel (Ovrette)
  • blood pressure medicine such as timolol, nadolol (Corgard), propranolol (Inderal), acebutolol (Sectral), carvedilol (Coreg), atenolol (Tenormin), betaxolol (Kerlone), bisoprolol (Zebeta), esmolol (Brevibloc), labetalol (Normodyne, Trandate), metoprolol (Lopressor, Toprol XL), methyldopa, pindolol, and sotalol (Betapace)
  • medicine that reduces the chance of blood clots forming such as clopidogrel (Plavix), dalteparin (Fragmin), dipyridamole (Persantine), enoxaparin (Lovenox), and heparin
  • cholesterol-lowering medicines such as atorvastatin (Lipitor), cholestyramine (Questran), colestipol (Colestid), ezetimibe (Zetia), ezetimibe/simvastatin (Vytorin), fenofibrate (TriCor), fluvastatin (Lescol), gemfibrozil (Lopid), lovastatin (Mevacor), pravastatin (Pravachol), and simvastatin (Zocor)
  • corticosteroids such as betamethasone (Celestone), cortisone, dexamethasone, fludrocortisone (Florinef), hydrocortisone (Cortef, Hydrocortone, A-HydroCort), methylprednisolone (Medrol), prednisone, prednisolone, and triamcinolone (Aristospan, Kenalog)
  • diabetes medicines such as chlorpropamide, glipizide (Glucotrol), glyburide (DiaBeta), metformin (Glucophage), pioglitazone (Actos), repaglinide (Prandin), rosiglitazone (Avandia), and tolbutamide (Tol-tab)
  • disulfiram (Antabuse)
  • diuretics (water pills) such as chlorthalidone and spironolactone (Aldactone)
  • gout medicines such as allopurinol (Zyloprim, Aloprim)
  • heart medicines such as amiodarone (Cordarone; Pacerone), propafenone (Rythmol), and quinidine
  • heartburn or ulcer medicines such as antacids, cimetidine (Tagamet), esomeprazole (Nexium), lansoprazole (Prevacid), omeprazole (Prilosec), rabeprazole (Aciphex), ranitidine (Zantac), and sucralfate (Carafate)
  • immunosuppressant medicine such as azathioprine (Imuran)
  • MAO inhibitor antidepressants such as isocarboxazid (Marplan), phenelzine (Nardil), selegiline (Eldepryl, Emsam), and tranylcypromine (Parnate) (Do not take this medicine and an MAO inhibitor within 14 days of each other.)
  • medicine for low blood sugar such as glucagon
  • medicines used to treat cancer such as capecitabine (Xeloda), cyclophosphamide (Cytoxan), fluorouracil (Adrucil, 5-FU), flutamide (Eulexin), gefitinib (Iressa), ifosfamide (Ifex), mercaptopurine (Purinethol, 6-MP), and tamoxifen (Nolvadex)
  • methylphenidate (Ritalin, Concerta, Metadate)
  • natural remedies such as agrimony, alfalfa, arnica, black cohosh, coenzyme Q10, cranberry, capsicum, chamomile, dandelion dong quai, fenugreek, feverfew, garlic, ginkgo biloba, ginger, ginseng, goldenseal, horse chestnut, licorice, nettle, passion flower, pau d'arco, red clover, SAMe, St. John's wort, sweet clover, and willow
  • orlistat (Xenical)
  • quinine
  • raloxifene (Evista)
  • sleeping pills such as chloral hydrate
  • SSRI antidepressants such as fluoxetine (Prozac, Sarafem), fluvoxamine (Luvox), paroxetine (Paxil), sertraline (Zoloft), and trazodone
  • thyroid medicine such as liothyronine (Cytomel, Triostat), levothyroxine (Levothroid, Levoxyl, Synthroid, Unithroid), methimazole (Tapazole), propylthiouracil, and thyroid (Armour Thyroid, Nature-Throid)
  • vitamins such as vitamin K, vitamin A, vitamin E, and large amounts of vitamin C

Do not eat large amounts of cranberries or drink a lot of cranberry juice or green tea while taking this medicine. Cranberries and green tea may affect the way this medicine works and may increase the risk of side effects.

While you are taking this medicine, eat a healthy balanced diet with about the same amount of vitamin K each day. Do not make big changes in your diet until you talk with your healthcare provider. Foods that have moderate to high amounts of vitamin K include brussel sprouts, kale, green tea, asparagus, avocado, broccoli, cabbage, cauliflower, collard greens, liver, soybean oil, soybeans, certain beans, mustard greens, peas (black-eyed peas, split peas, chick peas), turnip greens, parsley, green onions, spinach, and lettuce.

Do not drink alcohol while you are taking this medicine. Talk with your healthcare provider about this.

If you are not sure if your medicines might interact, ask your pharmacist or healthcare provider. Keep a list of all your medicines with you. List all the prescription medicines, nonprescription medicines, supplements, natural remedies, and vitamins that you take. Be sure that you tell all healthcare providers who treat you about all the products you are taking.

How should I store this medicine?

Store this medicine at room temperature. Keep the container tightly closed. Protect it from heat, high humidity, and bright light.


This advisory includes selected information only and may not include all side effects of this medicine or interactions with other medicines. Ask your healthcare provider or pharmacist for more information or if you have any questions.

Ask your pharmacist for the best way to dispose of outdated medicine or medicine you have not used. Do not throw medicine in the trash.

Keep all medicines out of the reach of children.

Do not share medicines with other people.


Developed by RelayHealth.
Medication Advisor 2012.1 published by RelayHealth.
Last modified: 2011-11-30
Last reviewed: 2011-11-30
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2012 RelayHealth and/or its affiliates. All rights reserved.
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