Generic name: Warfarin sodium.

Other brand names: Sofarin.

Coumadin is an anticoagulant/blood thinner. It works by decreasing the production of blood-clotting substances by the liver. 

Quick Facts About Coumadin


Used to treat and/or prevent blood clots: within a blood vessel; from reaching the lungs; or to prevent heart attack or stroke.

Coumadin Dosage

Take exactly as prescribed, adhere strictly to dosage schedule. Do not change drug brand without consulting your doctor.

  • Usual adult dose: 2 to 5 milligrams per day to start. Maintenance dose ranges from 2 to 10 milligrams per day. Dose is highly variable; doctor will individualize carefully for your specific needs.
  • Usual child dose: not prescribed for children under 18 years.
  • Missed dose: take as soon as possible, then go back to regular schedule. Do not double doses.

Coumadin Side Effects

Overdose symptoms:

blood in stools or urine, excessive menstrual bleeding, black stools, reddish or purplish spots on skin, excessive bruising, persistent bleeding from superficial injuries. If you suspect an overdose, immediately seek medical attention.

More common side effects: hemorrhage — symptoms include chest, abdomen, joint or other pain; difficult breathing or swallowing; headache; paralysis; shortness of breath; unexplained shock; unexplained swelling. Other common side effect: necrosis (gangrene).

Less common Coumadin side effects: abdominal and other cramping, allergic reactions, diarrhea, fever, hives, liver damage, loss of hair, nausea, purple toes, severe or long-lasting inflammation of the skin.


Inform your doctor before combining Coumadin with:

Acetaminophen (Tylenol), Allopurinol (Zyloprim), Aminosalicylic acid, Amiodarone hydrochloride (Cordarone), anabolic steroids such as Anadrol-50, antibiotics such as Cipro, Anistreplase (Eminase), Bromelains (Bromase), Chenodiol, Chloral hydrate (Noctec), Chlorpropamide (Diabinese), Chymotrypsin, Cimetidine (Tagamet), Clofibrate (Atromid-S), Dextrothyroxine (Choloxin), Diazoxide (Proglycem), Diflunisal (Dolobid), Disulfiram (Antabuse), diuretics such as Hydromox, Ethacrynic acid (Edecrin), Fenoprofen (Nalfon), Glucagon, hepatotoxic drugs, Ibuprofen (Motrin), Indomethacin (Indocin), influenza virus vaccine (Flu-Immune), Lovastatin (Mevacor), Mefenamic acid (Ponstel), Methyldopa (Aldomet), Methylphenidate (Ritalin), Metronidazole (Flagyl), Moconazole (Monistat), MAO inhibitors (antidepressants such as Nardil or Parnate), Moricizine hydrochloride (Ethmozine), Nalidixic acid (NegGram), Naproxen (Naprosyn), narcotics taken for long periods such as Demerol and Percocet, Pentoxifylline (Trental), Phenobarbital in drugs such as Donnatal, Phenylbutazone (Butazolidin), Phenytoin (Dilantin), Propafenone (Rythmol), Quinidine (Quinidex), Quinine (Quinamm), Ranitidine (Zantac), salicylates (Aspirin), Streptokinase (Streptase), sulfa drugs such as Bactrim and Septra, Sulfinpyrazone (Anturane), Sulindac (Clinoril), Tamoxifen (Nolvadex), thyroid drugs (Synthroid), Ticlopidine (Ticlid), Tolbutamide (Orinase), topical pain relievers such as Anbesol, Urokinase (Abbokinase). Drugs which may slow the blood-clotting process if taken with Coumadin include: adrenocortical steroids such as Prednisone, Aminoglutethimide (Cytadren), antacids such as Maalox, antihistamines such as Benadryl, barbiturates such as Phenobarbital, Carbamazepine (Tegretol), Chloral hydrate (Noctec), Chlordiazepoxide (Librium), Cholestyramine (Questran), diuretics such as Hydromox, Ethchlorvynol (Placidyl), Glutethimide (Doriden), Griseofulvin (Gris-PEG), Haloperidol (Haldol), Meprobamate (Miltown), Moricizine hydrochloride (Ethmozine), Nafcillin (Unipen), oral contraceptives, Paraldehyde, Primidone (Mysoline), Ranitidine (Zantac), Rifampin (Rifadin), Sucralfate (Carafate), Trazodone (Desyrel), vitamin C.

Do not eat large amounts of leafy green vegetables; they contain vitamin K, and may counteract the effects of Coumadin. Avoid alcohol, as well as any drastic change in diet. 

Special Cautions

Coumadin passes through the placental barrier, possibly causing fatal hemorrhage in the fetus. Reports of malformed babies born to mothers taking Coumadin, as well as spontaneous abortions and stillbirths. If pregnant or planning to become pregnant, inform your doctor immediately. May appear in breast milk, could affect a nursing baby.

No special precautions apply to seniors.

Not generally prescribed for children.

  • Do not take if you are being treated for: a tendency to hemorrhage, abnormal blood condition, aneurysms, bleeding tendencies (associated with ulceration of the stomach, intestines, respiratory tract, or genital or urinary system), eclampsia, excessive bleeding of brain blood vessels, inflammation due to bacterial infection of the membrane lining the heart, malignant hypertension, preeclampsia, pregnancy, recent or contemplated traumatic surgery, recent or future central nervous system or eye surgery, threatened abortion.
  • Blood clot risk increased if you have: an infectious disease or intestinal disorder, family history of blood clots, dental procedures, inflammation of a blood vessel, moderate to severe high blood pressure, moderate to severe kidney or liver dysfunction, polycythemia vera, severe allergic disorders, severe diabetes, trauma resulting in internal bleeding.
  • Doctor should monitor the time it takes for your blood to clot on a continuous basis.
  • Notify your doctor if you experience: diarrhea; infection or fever; pain, swelling or discomfort; prolonged bleeding from cuts; increased menstrual flow; vaginal bleeding; nosebleeds; bleeding of gums from brushing; unusual bleeding or bruising; red or dark brown urine; or red or tarry black stool.
  • Monitor for purple toes syndrome, which may occur 3 to 10 weeks after taking Coumadin.
  • If you have congestive heart failure, you should be monitored by your doctor for sensitivity to Coumadin.
  • Serious risk of hemorrhage and gangrene associated with Coumadin, resulting in death or permanent disability.
  • Should carry identification card indicating you are taking Coumadin.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Coumadin side effects, please contact your healthcare provider.