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Warfarin (Warfarin Sodium) - Summary



Warfarin sodium can cause major or fatal bleeding. Bleeding is more likely to occur during the starting period and with a higher dose (resulting in a higher INR). Risk factors for bleeding include high intensity of anticoagulation (INR >4.0), age ≥65, highly variable INRs, history of gastrointestinal bleeding, hypertension, cerebrovascular disease, serious heart disease, anemia, malignancy, trauma, renal insufficiency, concomitant drugs (see PRECAUTIONS) and long duration of warfarin therapy. Regular monitoring of INR should be performed on all treated patients. Those at high risk of bleeding may benefit from more frequent INR monitoring, careful dose adjustment to desired INR, and a shorter duration of therapy. Patients should be instructed about prevention measures to minimize risk of bleeding and to report immediately to physicians signs and symptoms of bleeding (see PRECAUTIONS: Information for Patients).



Warfarin sodium is an anticoagulant which acts by inhibiting vitamin K-dependent coagulation factors.

Warfarin sodium tablets are indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, and pulmonary embolism.

Warfarin sodium tablets are indicated for the prophylaxis and/or treatment of the thromboembolic complications associated with atrial fibrillation and/or cardiac valve replacement.

Warfarin sodium tablets are indicated to reduce the risk of death, recurrent myocardial infarction, and thromboembolic events such as stroke or systemic embolization after myocardial infarction.

See all Warfarin indications & dosage >>


Media Articles Related to Warfarin

Study: Aspirin Might Work Instead of Warfarin for Deep Vein Clots
Source: MedicineNet Deep Vein Thrombosis Specialty [2014.08.27]
Title: Study: Aspirin Might Work Instead of Warfarin for Deep Vein Clots
Category: Health News
Created: 8/26/2014 12:35:00 PM
Last Editorial Review: 8/27/2014 12:00:00 AM

Comparing the New Blood Thinners to Warfarin
Source: MedicineNet enoxaparin Specialty [2013.06.03]
Title: Comparing the New Blood Thinners to Warfarin
Category: Health News
Created: 6/1/2013 11:00:00 AM
Last Editorial Review: 6/3/2013 12:00:00 AM

Clot-Buster Doesn't Raise Bleeding Risk in Warfarin Patients: Study
Source: MedicineNet alteplase Specialty [2012.05.11]
Title: Clot-Buster Doesn't Raise Bleeding Risk in Warfarin Patients: Study
Category: Health News
Created: 5/10/2012 6:05:00 PM
Last Editorial Review: 5/11/2012 12:00:00 AM

Herbal Supplements, Warfarin Can Be Hazardous Mix
Source: MedicineNet Saw Palmetto Specialty [2010.05.14]
Title: Herbal Supplements, Warfarin Can Be Hazardous Mix
Category: Health News
Created: 5/13/2010 4:10:00 PM
Last Editorial Review: 5/14/2010

Aspirin as effective as warfarin and safer in stroke prevention
Source: The Doctors Lounge - Neurology
Intracranial stenosis is caused by atherosclerosis - fatty deposits that build up on the inner walls of the arteries and restrict blood flow.

more news >>

Published Studies Related to Warfarin

A placebo-controlled randomized trial of warfarin in idiopathic pulmonary fibrosis. [2012]
and declines in FVC... CONCLUSIONS: This study did not show a benefit for warfarin in the treatment of

Risks for Stroke, Bleeding, and Death in Patients With Atrial Fibrillation Receiving Dabigatran or Warfarin in Relation to the CHADS2 Score: A Subgroup Analysis of the RE-LY Trial. [2011.11.15]
Background: CHADS(2) is a simple, validated risk score for predicting the risk for stroke in patients with atrial fibrillation not treated with anticoagulants.

Apixaban versus warfarin in patients with atrial fibrillation. [2011.09.15]
BACKGROUND: Vitamin K antagonists are highly effective in preventing stroke in patients with atrial fibrillation but have several limitations. Apixaban is a novel oral direct factor Xa inhibitor that has been shown to reduce the risk of stroke in a similar population in comparison with aspirin... CONCLUSIONS: In patients with atrial fibrillation, apixaban was superior to warfarin in preventing stroke or systemic embolism, caused less bleeding, and resulted in lower mortality. (Funded by Bristol-Myers Squibb and Pfizer; ARISTOTLE ClinicalTrials.gov number, NCT00412984.).

Rivaroxaban versus warfarin in nonvalvular atrial fibrillation. [2011.09.08]
BACKGROUND: The use of warfarin reduces the rate of ischemic stroke in patients with atrial fibrillation but requires frequent monitoring and dose adjustment. Rivaroxaban, an oral factor Xa inhibitor, may provide more consistent and predictable anticoagulation than warfarin... CONCLUSIONS: In patients with atrial fibrillation, rivaroxaban was noninferior to warfarin for the prevention of stroke or systemic embolism. There was no significant between-group difference in the risk of major bleeding, although intracranial and fatal bleeding occurred less frequently in the rivaroxaban group. (Funded by Johnson & Johnson and Bayer; ROCKET AF ClinicalTrials.gov number, NCT00403767.).

A multicenter, randomized trial comparing heparin/warfarin and acetylsalicylic acid as primary thromboprophylaxis for 2 years after the Fontan procedure in children. [2011.08.02]
OBJECTIVES: The purpose of this study was to compare the safety and efficacy of acetylsalicylic acid (ASA) and warfarin for thromboprophylaxis after the Fontan procedure. BACKGROUND: Fontan surgery is the definitive palliation for children with single-ventricle physiology. Thrombosis is an important complication; the optimal thromboprophylaxis strategy has not been determined... CONCLUSIONS: There was no significant difference between ASA and heparin/warfarin as primary thromboprophylaxis in the first 2 years after Fontan surgery. The thrombosis rate was suboptimal for both regimens, suggesting alternative approaches should be considered. (International Multi Centre Randomized Clinical Trial Of Anticoagulation In Children Following Fontan Procedures; NCT00182104). Copyright (c) 2011 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

more studies >>

Clinical Trials Related to Warfarin

Duloxetine - Warfarin Pharmacodynamic Study [Completed]
To evaluate the blood clotting effects of multiple doses of warfarin at steady state when taken at the same time as multiple doses of duloxetine as measured by changes in the International Normalised Ratio.

PerMIT: Warfarin: A Trial Comparing Usual Care Warfarin Initiation to PerMIT Pharmacogenetic Guided Warfarin Therapy [Recruiting]
Warfarin is the most commonly used oral anticoagulant medicine (blood thinner). Although this medicine works well, it is difficult to know how much medicine a patient needs. Many things affect how much medicine a patient needs and doses can be very different from patient to patient. It is important for patients to get the right dose to prevent clotting or bleeding problems that can happen with this medicine if the dose is too low or too high. These problems can be life-threatening. To help find the right dose, patients on warfarin must have frequent blood tests to measure how well the medicine is working. The investigators know differences in people's genes can affect how much warfarin medicine someone needs, but they don't yet know with certainty how to use this information in making patient care decisions. The hypothesis of this study is that using a patients warfarin related genetic information incorporated into a computer algorithm to be used by a warfarin provider will lead to better warfarin management compared to usual care.

A Drug-Drug Interaction Study Between AZD9668 and Warfarin to Study the Effect of AZD9668 on the Metabolism and Effect of Warfarin [Not yet recruiting]
The primary purpose of this study is to determine whether the treatment with AZD9668 will affect the metabolism and effect of Warfarin.

Applying Pharmacogenetic Algorithms to Individualize Dosing of Warfarin [Recruiting]
The purpose of this study is to determine whether DNA analysis improves the efficiency of dosing and safety in patients who are being started on warfarin therapy. Warfarin, a blood thinner (anticoagulant) prescribed to 1-2 million patients in the US, is a leading cause of drug-related adverse events (e. g., severe bleeding), in large part due to dramatic (20-fold) differences between individuals in dose requirements. At least half of this variability now can be explained by 3 common genetic variants, age, body size, and sex; however, warfarin therapy continues to begin with the same dose in every patient with the correct individual dose determined by trial and error. This study proposes to determine genetic variations the same day from DNA simply obtained by swabbing the inside of the cheek and use this information to determine the proper dose regimen individually in each patient. The aim is to show that the investigators can achieve more rapid, efficient, and safe dosing in up to 500-1000 individuals who are initiating warfarin therapy for various clotting disorders across a large healthcare system in order to demonstrate improved dosing effectiveness, efficiency, and safety with genetic-based dosing, which could lead to a nationwide application resulting in as much as a $1 billion dollar annual benefit in healthcare outcomes.

A Drug-Drug Interaction Study to Study the Effect of AZD1981 on Warfarin [Not yet recruiting]
The primary purpose of this study is to determine whether the treatment with AZD1981 affect the exposure of Warfarin.

more trials >>

Reports of Suspected Warfarin Side Effects

International Normalised Ratio Increased (9)Drug Interaction (6)Drug Ineffective (2)Skin Exfoliation (2)Pyrexia (2)Completed Suicide (2)Hallucination (2)Toxicity TO Various Agents (2)Renal Impairment (2)Diarrhoea (2)more >>


Based on a total of 1 ratings/reviews, Warfarin has an overall score of 6. The effectiveness score is 8 and the side effect score is 6. The scores are on ten point scale: 10 - best, 1 - worst.

Warfarin review by 44 year old female patient

Overall rating:  
Effectiveness:   Considerably Effective
Side effects:   Moderate Side Effects
Treatment Info
Condition / reason:   heart condition
Dosage & duration:   3 mg. warfarin taken 1 time daily for the period of 3 years
Other conditions:   none
Other drugs taken:   none
Reported Results
Benefits:   Taking 3 mg of warfarin sufficiently thinned my blood so that I did not find it difficult to do everyday tasks. I immediately felt better after I started the regimen in the spring of 2003. My cough went away and I had a lot more energy. I took this regimen for about 3 years, everyday. I also found it easier to concentrate and think (what was I doing before it???) It was as if my brain cleared up or something. I breathed easier and I was more willing to tackle regular household chores. I worked over 50 hours/week before and during this treatment.
Side effects:   The side effects of warfarin on me did not become apparent until a couple of years later. I started feeling weak and I bruised easily. I acquired more broken blood vessels/capillaries veins in my feet and calves. I was tired and started feeling cranky. I stopped taking warfarin for 6 months but then went back to it after I had the old feeling of "thick" blood. During the 6 months that I wasn't taking warfarin, I felt better, had more energy. But then the downside: my blood was getting too thick and I was starting to get headaches. So I went back on it. This time my doctor said I might have to increase dosage to 4 mg. since I hadn't been taking the warfarin. However, when I had my thrombin checked, I was okay at 3 mg.; I took this for another 3 months and then started feeling the old way and quit again. The same scenario was repeated (started feeling like I had "thick" blood and now I had increasingly bad headaches). I went back on 3 mg. of warfarin in August of this year but only took them for 3 months. Then I started a vitamin/mineral/COQ10 regimen and stuck with it and am still doing that. I credit most of the perfect blood feeling (for lack of a better term) to Vitamin E and the fact that I also changed my diet. I try to eat a lot of veggies and fruits, and I have been a vegetarian for almost two years (not super strict - but I feel disgusted about eating meat and therefore never eat it unless it is buried in some food. I do eat salmon and tuna. The final straw for me with warfarin was that I started feeling really mad about things. The littlest things would make me angry, anger that was way out of proportion to the incident. When my teenaged daughter started crying after I ripped into her for staying longer at a social visit, and I heard my words echoing in my house, I knew that was it. I quit warfarin and started taking 81 mg. of aspirin daily (I had a headache every morning after I went off warfarin). I started the vit./min. regimen in November, gradually adding supplements as I learned about their benefits, but it wasn't until 3-4 weeks ago that I realized I wasn't having any headaches and I was able to stop taking 81 mg. of aspirin. Also, since starting the stricter diet and the vit./min. supplements (also some herbs), I have not had an anger "fit" (of course, I am also more prone to control my anger because I really didn't like how I had been), I do not feel depressed. I have told everyone in my family about this because it seems so remarkable. Why didn't the doctors tell me?
Comments:   Treatment consisted of simply taking 3 mg. of warfarin daily and getting my blood thrombin checked every two months. I was not a very good patient about getting my blood thr. checked so I'm sure when I was feeling weak and bruised/bled so easily, my blood was getting too thin. And then when I would quit the warfarin for several weeks, sometimes months at a time, my blood would get too thick. I really like my doctor though, because he tells me to do what makes me feel best, and I think that's smart advice. I must say add that I always loved the feeling of donating blood before I took warfarin because it gave me the same feeling as I initially had with warfarin (at the very beginning of my treatment). I would like to donate blood now but they don't let me because I don't weigh enough (which makes no sense at all). Couldn't they take less blood? Who determined how much blood you can give anyway?

See all Warfarin reviews / ratings >>

Page last updated: 2014-08-27

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