Warfarin Side Effects

Brand Names: Coumadin, Jantoven

Please note - some side effects for Warfarin may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Warfarin - for the Consumer

Warfarin

All medicines may cause side effects, but many people have no, or minor, side effects. No COMMON side effects have been reported with Warfarin . Seek medical attention right away if any of these SEVERE side effects occur when using Warfarin:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); back, side, muscle, joint, or stomach pain; black, tarry, or bloody stools; blood in the urine (pink or brown urine); bloody or coffee ground-like vomit; chest pain; decreased urination; dizziness; fainting; fever; numbness or tingling; pain, unusual color, or temperature change in any area of the body; pale skin; purple, dark, or painful toes; shortness of breath; skin sores or ulcers; stroke symptoms (eg, confusion, slurred speech, vision problems, one-sided weakness); sudden severe pain in your legs, feet, or toes; trouble swallowing; unexplained swelling; unusual bruising or bleeding (eg, nosebleed, unusual bleeding from gums, increased bleeding from cuts, increased menstrual or vaginal bleeding, coughing up blood, bleeding at the injection site); unusual headache or weakness; unusual pain, swelling, or discomfort; wounds or sores that do not heal properly; yellowing of the skin or eyes.

Warfarin Tablets

All medicines may cause side effects, but many people have no, or minor, side effects. No COMMON side effects have been reported with Warfarin. Seek medical attention right away if any of these SEVERE side effects occur when using Warfarin Tablets:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); back, side, muscle, joint, or stomach pain; black, tarry, or bloody stools; blood in the urine (pink or brown urine); bloody or coffee ground-like vomit; chest pain; decreased urination; dizziness; fainting; fever; numbness or tingling; pain, unusual color, or temperature change in any area of the body; pale skin; purple, dark, or painful toes; shortness of breath; skin sores or ulcers; stroke symptoms (eg, confusion, slurred speech, vision problems, one-sided weakness); sudden severe pain in your legs, feet, or toes; trouble swallowing; unexplained swelling; unusual bruising or bleeding (eg, nosebleed, unusual bleeding from gums, increased bleeding from cuts, increased menstrual or vaginal bleeding, coughing up blood); unusual headache or weakness; unusual pain, swelling, or discomfort; wounds or sores that do not heal properly; yellowing of the skin or eyes.

Warfarin Side Effects - for the Professional

Warfarin

Potential adverse reactions to Warfarin sodium tablets may include:

• Fatal or nonfatal hemorrhage from any tissue or organ. This is a consequence of the anticoagulant effect. The signs, symptoms, and severity will vary according to the location and degree or extent of the bleeding. Hemorrhagic complications may present as paralysis; paresthesia; headache, chest, abdomen, joint, muscle or other pain; dizziness; shortness of breath, difficult breathing or swallowing; unexplained swelling; weakness; hypotension; or unexplained shock. Therefore, the possibility of hemorrhage should be considered in evaluating the condition of any anticoagulated patient with complaints which do not indicate an obvious diagnosis. Bleeding during anticoagulant therapy does not always correlate with PT/INR.
• Bleeding which occurs when the PT/INR is within the therapeutic range warrants diagnostic investigation since it may unmask a previously unsuspected lesion, e.g., tumor, ulcer, etc.
• Necrosis of skin and other tissues.
• Adverse reactions reported infrequently include: hypersensitivity/allergic reactions, including anaphylactic reactions, systemic cholesterol microembolization, purple toes syndrome, hepatitis, cholestatic hepatic injury, jaundice, elevated liver enzymes, hypotension, vasculitis, edema, anemia, pallor, fever, rash, dermatitis, including bullous eruptions, urticaria, angina syndrome, chest pain, abdominal pain including cramping, flatulence/bloating, fatigue, lethargy, malaise, asthenia, nausea, vomiting, diarrhea, pain, headache, dizziness, loss of consciousness, syncope, coma, taste perversion, pruritus, alopecia, cold intolerance, and paresthesia including feeling cold and chills.

Rare events of tracheal or tracheobronchial calcification have been reported in association with long-term Warfarin therapy. The clinical significance of this event is unknown.

Priapism has been associated with anticoagulant administration, however, a causal relationship has not been established.

Side Effects by Body System

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

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.

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 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.

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 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.

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