Warfarin

generic for Jantoven

Warfarin Side Effects

Nausea, loss of appetite, or stomach/abdominal pain may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

This medication can cause serious bleeding if it affects your blood clotting proteins too much (shown by unusually high INR lab results). Even if your doctor stops your medication, this risk of bleeding can continue for up to a week. Tell your doctor right away if you have any signs of serious bleeding, including: unusual pain/swelling/discomfort, unusual/easy bruising, prolonged bleeding from cuts or gums, persistent/frequent nosebleeds, unusually heavy/prolonged menstrual flow, pink/dark urine, coughing up blood, vomit that is bloody or looks like coffee grounds, severe headache, dizziness/fainting, unusual or persistent tiredness/weakness, bloody/black/tarry stools, chest pain, shortness of breath, difficulty swallowing.

Tell your doctor right away if any of these unlikely but serious side effects occur: persistent nausea/vomiting, severe stomach/abdominal pain, yellowing eyes/skin.

This drug rarely has caused very serious (possibly fatal) problems if its effects lead to small blood clots (usually at the beginning of treatment). This can lead to severe skin/tissue damage that may require surgery or amputation if left untreated. Patients with certain blood conditions (protein C or S deficiency) may be at greater risk. Get medical help right away if any of these rare but serious side effects occur: painful/red/purplish patches on the skin (such as on the toe, breast, abdomen), signs of kidney problems (such as change in the amount of urine), vision changes, confusion, slurred speech, weakness on one side of the body.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
  • anemia
  • agranulocytosis
  • leukopenia
  • cholesterol embolism
  • vasculitis
  • hemorrhage
  • hepatitis
  • hematuria
  • allergic dermatitis
  • pruritus of skin
  • alopecia
  • urticaria
  • chills
  • dysgeusia
  • skin rash
  • pallor
  • dermal necrosis
  • nausea
  • vomiting
  • flatulence
  • diarrhea
  • abdominal pain with cramps
  • abdominal distension
  • abnormal hepatic function tests
  • anaphylaxis
  • hypersensitivity drug reaction
  • cholestatic hepatitis
  • gangrene
  • tissue necrosis
  • jaundice
  • calcification of trachea
  • calcification of bronchus
  • calciphylaxis

Drug Interactions

See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Warfarin interacts with many prescription, nonprescription, vitamin, and herbal products. This includes medications that are applied to the skin or inside the vagina or rectum. The following interactions listed do not contain all possible drug interactions. The interactions with warfarin usually result in an increase or decrease in the "blood-thinning" (anticoagulant) effect. Your doctor or other health care professional should closely monitor you to prevent serious bleeding or clotting problems. While you are taking warfarin, it is very important to tell your doctor or pharmacist of any changes in medications, vitamins, or herbal products that you are taking.

Some products that may interact with this drug include: imatinib, mifepristone.

Aspirin, aspirin-like drugs (salicylates), and nonsteroidal anti-inflammatory drugs (NSAIDs such as ibuprofen, naproxen, celecoxib) may have effects similar to warfarin. These drugs may increase the risk of bleeding problems if taken during treatment with warfarin. Carefully check all prescription/nonprescription product labels (including drugs applied to the skin such as pain-relieving creams) since the products may contain NSAIDs or salicylates. Talk to your doctor about using a different medication (such as acetaminophen) to treat pain/fever. Low-dose aspirin and related drugs (such as clopidogrel, ticlopidine) should be continued if prescribed by your doctor for specific medical reasons such as heart attack or stroke prevention. Consult your doctor or pharmacist for more details.

This medication may interfere with a certain laboratory test to measure theophylline levels, possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.