DrugLib.com — Drug Information Portal

Rx drug information, pharmaceutical research, clinical trials, news, and more

Warfarin (Warfarin Sodium) - Summary



  • Warfarin sodium can cause major or fatal bleeding [see Warnings and Precautions].
  • Perform regular monitoring of INR in all treated patients [see Dosage and Administration].
  • Drugs, dietary changes, and other factors affect INR levels achieved with warfarin sodium therapy [see Drug Interactions].
  • Instruct patients about prevention measures to minimize risk of bleeding and to report signs and symptoms of bleeding [see Patient Counseling Information].


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

Warfarin sodium tablets,USP are indicated for:

  • Prophylaxis and treatment of venous thrombosis and its extension, pulmonary embolism (PE).
  • Prophylaxis and treatment of thromboembolic complications associated with atrial fibrillation (AF) and/or cardiac valve replacement.
  • Reduction in the risk of death, recurrent myocardial infarction (MI), and thromboembolic events such as stroke or systemic embolization after myocardial infarction.

Limitations of Use

Warfarin sodium tablets, USP have no direct effect on an established thrombus, nor does it reverse ischemic tissue damage. Once a thrombus has occurred, however, the goals of anticoagulant treatment are to prevent further extension of the formed clot and to prevent secondary thromboembolic complications that may result in serious and possibly fatal sequelae.

See all Warfarin indications & dosage >>


Media Articles Related to Warfarin

Genotyping Lowers Warfarin Risk in Hip or Knee Replacement
Source: Medscape Anesthesiology Headlines [2017.09.26]
Considering variants of three genes that affect response to warfarin improved the safety of using the drug.
Medscape Medical News

more news >>

Published Studies Related to Warfarin

Genetics and the clinical response to warfarin and edoxaban: findings from the randomised, double-blind ENGAGE AF-TIMI 48 trial. [2015]
anticoagulant rather than warfarin... INTERPRETATION: CYP2C9 and VKORC1 genotypes identify patients who are more likely

Relationship between time in therapeutic range and comparative treatment effect of rivaroxaban and warfarin: results from the ROCKET AF trial. [2014]
CONCLUSIONS: The treatment effect of rivaroxaban compared with warfarin for the

Outcomes of temporary interruption of rivaroxaban compared with warfarin in patients with nonvalvular atrial fibrillation: results from the rivaroxaban once daily, oral, direct factor Xa inhibition compared with vitamin K antagonism for prevention of stroke and embolism trial in atrial fibrillation (ROCKET AF). [2014]
CONCLUSIONS: TI of oral anticoagulation is common and is associated with

Efficacy and safety of rivaroxaban compared with warfarin in patients with peripheral artery disease and non-valvular atrial fibrillation: insights from ROCKET AF. [2014]
CONCLUSION: Patients with PAD in ROCKET AF did not have a statistically

Apixaban vs. warfarin with concomitant aspirin in patients with atrial fibrillation: insights from the ARISTOTLE trial. [2014]
CONCLUSION: Apixaban had similar beneficial effects on stroke or systemic

more studies >>

Clinical Trials Related to Warfarin

Warfarin Adverse Event Reduction For Adults Receiving Genetic Testing at Therapy INitiation (WARFARIN) [Recruiting]
The WARFARIN Study is a clinical trial designed to determine if the use of genetic information related to warfarin sensitivity can help create a dose of warfarin that will result in less hospitalizations and deaths related to warfarin.

Drug Interaction Study of Isavuconazole and Warfarin in Healthy Male Subjects [Completed]
The purpose of this study is to assess the effect of multiple doses of isavuconazole on the pharmacokinetics (PK) of warfarin after single dose administration.

Applying Pharmacogenetic Algorithms to Individualize Dosing of Warfarin [Completed]
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 United States, 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.

Pharmacogenetics of Warfarin Induction and Inhibition [Completed]
This research study will help determine how a person's genetic makeup affects their response to drugs, the ability of the body to break down drugs, and their potential to experience an interaction between drugs. The investigators are investigating the drug interactions with the commonly used anticoagulant drug called warfarin. Warfarin is used for the treatment and prevention of life-threatening abnormal blood clots such as deep vein thrombosis, heart attacks, and strokes. The investigators chose warfarin for this study because it is a commonly used drug and must be monitored closely to avoid side effects. The investigators are interested in studying whether individuals with certain genetic profiles react differently to warfarin when it is combined with other drugs. This research is being done to see if certain genetic profiles require us to adjust warfarin doses differently than is needed for the general population. Genetic profiles of subjects are determined from their participation in the Pharmacogenetics Registry study (investigator Richard Brundage, University of Minnesota). The study hypothesis is: Functionally defective CYP2C9 alleles attenuate the warfarin-fluconazole inhibitory interaction and exacerbate the warfarin-rifampin inductive interaction.

Genetic Response to Warfarin in Healthy Subjects [Completed]
The purpose of this study is to determine the importance of genetic differences on individuals' response to warfarin in a group of healthy subjects. Warfarin is also known by the "trade name" Coumadin and is in a class of medications called anticoagulants or "blood thinners." Warfarin works by reducing the blood's ability to make clots. It is used to stop blood clots from forming or growing larger in your blood and blood vessels. Warfarin is prescribed for many conditions, including for people with certain types of irregular heartbeat, people with replacement or mechanical heart valves, people who have suffered a heart attack, people who have had orthopedic surgery, or who have a history of having blood clots. Warfarin is used to prevent or treat deep vein thrombosis (swelling and blood clot in a vein), pulmonary embolism (a blood clot in the lung), and strokes (a blood clot in the brain). Researchers have found that certain genes may affect how a person's body will break down or react to warfarin. If genetic information can help doctors better determine the best dose of warfarin before it is first given, this may help the doctors get patients to the correct levels of blood thinning and thereby reduce the risk of bleeding or the risk of developing a blood clot. The expectation of this study is that this information will ultimately improve warfarin therapy while lessening the risks associated with dosing errors. This study is considered investigational because the subjects are healthy and not being prescribed warfarin for clinical care.

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: 2017-09-26

-- advertisement -- The American Red Cross
Home | About Us | Contact Us | Site usage policy | Privacy policy

All Rights reserved - Copyright DrugLib.com, 2006-2017