Coumadin Side Effects

Generic Name: warfarin

Note: This page contains information about the side effects of warfarin. Some of the dosage forms included on this document may not apply to the brand name Coumadin.

Not all side effects for Coumadin may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to warfarin: oral tablet

In addition to its needed effects, some unwanted effects may be caused by warfarin (the active ingredient contained in Coumadin). In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking warfarin:

Less common
  • Abdominal or stomach pain with cramping
  • 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
  • shortness of breath
  • 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
  • light-colored stools
  • loss of appetite
  • nausea and vomiting
  • pain in the toes
  • pain, redness, or sloughing of the skin
  • pale skin
  • skin blisters
  • skin rash
  • small red or purple spots on the skin
  • stomach pain
  • swelling of the eyes or eyelids
  • tightness in the chest or wheezing
  • troubled breathing with exertion
  • unpleasant breath odor
  • unusual bleeding or bruising
  • upper right abdominal or stomach pain
  • vomiting of blood
  • yellow eyes and skin
Incidence not known
  • Painful or prolonged erection of the penis

Some of the side effects that can occur with warfarin may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

Less common
  • Joint pain
  • muscle pain
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

For Healthcare Professionals

Applies to warfarin: compounding powder, intravenous powder for injection, oral tablet

Hematologic

Hematologic side effects including occult and overt bleeding or hemorrhage at any site have been reported the most frequently. Bleeding complications may present as paralysis, paresthesia, headache, chest, abdominal, joint, muscle or other pain, dizziness, shortness of breath, difficulty breathing or swallowing, unexplained swelling, weakness, hypotension, or unexplained shock. Bleeding may result in hematomas, melena, hematuria, ecchymoses, epistaxis, and hematemesis. Spontaneous intraspinal hematomas, spinal cord hemorrhage, gastrointestinal hemorrhage, intracranial hemorrhage, ocular hemorrhage, intra-abdominal hemorrhage, hemopericardium, compartment syndrome following blunt trauma, and other serious bleeding events have been reported. Anemia has been reported infrequently.

Warfarin-induced intracranial hemorrhage is associated with a high rate of mortality and disability compared with extracranial hemorrhages.

Hematologic risk factors have included history of stroke, a serious comorbid condition, a history of gastrointestinal bleeding, atrial fibrillation, advanced age, and concomitant use of aspirin. In addition, patients with genetic variations in the CYP450 2C9 and VKORC1 enzymes are at a higher risk of bleeding than those without the variation.

A meta-analysis of five randomized controlled trials compared the efficacy and safety of combined oral anticoagulation and antiplatelet therapy versus oral anticoagulants alone after prosthetic heart valve replacement and found an increased risk of general hemorrhage (65%) and gastrointestinal hemorrhage (250%). Embolism and stroke were significantly decreased. The authors conclude that the benefits of decreased risk of thromboembolic events outweigh the toxic effects of combined anticoagulation and antiplatelet therapy.

The results of large observational cohort study (n=13,559) indicate that in patients with nonvalvular atrial fibrillation, the risk of major hemorrhage increases with age, particularly intracranial hemorrhage, whether or not they are receiving warfarin. In patients aged 80 and older the risk of intracranial hemorrhage increases sharply. Also, this study found that among anticoagulated patients with atrial fibrillation, intracranial hemorrhages were responsible for nearly 90% of the deaths from warfarin-associated hemorrhage and the majority of disability among survivors.

Dermatologic

Warfarin-induced skin necrosis predominantly affects obese women (4-fold greater occurrence in women) and typically occurs within 10 days of the initiation of therapy, but has occurred after several months or several years of therapy. The majority of lesions (80%) occur in areas with abundant adipose such as the thighs, breasts, abdomen, buttocks, and the extremities. The lesions are usually painful, abrupt in onset, erythematous, purpuric, and sharply demarcated. The proposed mechanism of warfarin-induced skin necrosis involves an imbalance between protein C or protein S and vitamin K-dependent clotting factors. The lesions may resolve spontaneously or progress to form hemorrhagic bullae with subsequent necrosis. Generally, warfarin (the active ingredient contained in Coumadin) is withheld; however, discontinuation does not affect lesion progression. Some patients have safely resumed warfarin therapy, but the recommended management in patients who require long-term anticoagulation is resumption of warfarin at a lower dose in conjunction with heparin bridge therapy. The dosage of warfarin should be slowly titrated until a therapeutic INR is reached.

One case of warfarin-induced skin necrosis of the eyelids has been reported. In this case, the patient developed bilateral periorbital ecchymoses with full-thickness necrotic lesions in the medial canthal region.

Dermatologic side effects including necrosis of the skin and other tissues have been reported in 0.1% to 1.0% of patients. Dermatitis, urticaria, alopecia, rash, bullous eruptions, pruritus, and pallor have been reported infrequently.

Other

Other side effects have been reported infrequently. These have included purple toe syndrome.

Cardiovascular

Cardiovascular side effects have included systemic atheroemboli and cholesterol microemboli, which present with a variety of signs and symptoms. These have included purple toe syndrome, livedo reticularis (blue tingeing of the skin), rash, gangrene, abrupt and intense pain in the leg, foot, or toes, foot ulcers, myalgia, penile gangrene, abdominal pain, flank or back pain, hematuria, renal insufficiency, hypertension, cerebral ischemia, spinal cord infarction, pancreatitis, symptoms simulating polyarteritis, or any other sequelae of vascular compromise due to embolic occlusion. Hemopericardium and cardiac tamponade have also been reported. Hypotension, edema, angina syndrome, and chest pain have been reported infrequently.

Hepatic

Hepatic side effects have been reported infrequently. These have included jaundice, intrahepatic cholestasis, hepatitis, and elevated liver enzymes.

Renal

Renal side effects have been reported infrequently. These have included hematuria, acute renal failure due to interstitial nephritis, and renal hematomas.

Gastrointestinal

A meta-analysis of five randomized controlled trials compared the efficacy and safety of combined oral anticoagulation and antiplatelet therapy versus oral anticoagulants alone after prosthetic heart valve replacement and found an increased risk of general hemorrhage (65%) and gastrointestinal hemorrhage (250%). Embolism and stroke were significantly decreased. The authors conclude that the benefits of decreased risk of thromboembolic events outweigh the toxic effects of combined anticoagulation and antiplatelet therapy.

Gastrointestinal side effects have been reported infrequently. Nausea, diarrhea, abdominal cramping, vomiting, and flatulence/bloating have been reported. Gastrointestinal bleed has occurred when warfarin was combined with aspirin for antithrombotic effects after placement of heart valves.

Genitourinary

Warfarin-induced priapism has been reported. In one case report, a 16 year old male patient had been treated with warfarin (the active ingredient contained in Coumadin) for a deep venous thrombosis in his leg. The patient experienced a hypercoagulable state upon initiation of warfarin therapy because he also had an undocumented protein C deficiency. This led to an increased risk of thromboembolism that manifested as priapism and skin necrosis.

Genitourinary side effects have included priapism.

Hypersensitivity

Hypersensitivity reactions including anaphylactic reactions have been reported infrequently. A case of leukocytoclastic cutaneous vasculitis has been reported.

Nervous system

Nervous system side effects have been reported rarely. These have included fever, fatigue, lethargy, malaise, asthenia, pain, headache, dizziness, taste perversion, cold intolerance, and paresthesia including feeling cold and chills, syncope, loss of consciousness, and coma.

Respiratory

Respiratory side effects have been reported rarely. These have included tracheal or tracheobronchial calcification.

Ocular

Ocular side effects have included subconjunctival hemorrhage and retinal hemorrhage.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. Drugs.com does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. 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 substances you are taking, check with your doctor, nurse, or pharmacist.

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