All About Warfarin For Nurses


  • Warfarin is an anticoagulant medication used to prevent and treat various thromboembolic conditions; understanding its indications, pharmacokinetics, contraindications, and drug interactions is essential for nurses. 
  • Nurses must closely monitor patients on warfarin therapy, including INR values, signs of bleeding, and potential drug interactions, to ensure safe and effective administration. 
  • Educating patients on the importance of regular follow-ups and INR monitoring is crucial for minimizing the risks associated with warfarin treatment and optimizing patient outcomes.

Mariya Rizwan

Pharm. D.

March 21, 2023
Simmons University

As a nurse, it is essential to be well-versed in the medications you administer to patients, particularly when it comes to high-risk medications such as anticoagulants. Warfarin, a commonly prescribed anticoagulant, plays a crucial role in preventing and treating blood clots.  

This blog post aims to provide a comprehensive overview of warfarin, including its indications, pharmacokinetics, contraindications, and potential drug interactions.  

Additionally, we will discuss crucial nursing considerations to ensure patient safety and optimal therapeutic outcomes. By understanding the complexities of warfarin therapy, you can better care for your patients and help them navigate the challenges associated with this medication. 


warfarin for nurses

A Quick Overview of Warfarin

Warfarin is indicated in conditions such as: 

  • Prophylaxis and treatment of thromboembolic disorders  
  • Prophylaxis and treatment of embolic complications arising from atrial fibrillation or valve replacement 
  • Risk reduction of a systemic embolism following a myocardial infarction 
  • Off-label use as an adjunct treatment in transient ischemic attacks

Warfarin is available under the brand names Coumadin and Jantoven. Do not confuse Coumadin with Kemadrin, or Jantoven with Janumet or Januvia. As a nurse, you must know that they are different drugs.  

Coumadin and Jantoven are available in strengths 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg, and 10 mg.

How Does Warfarin Behave?

Warfarin is a vitamin K antagonist. It interferes with the synthesis of vitamin K-dependent clotting factors in the liver and causes their depletion. Those clotting factors include coagulation factors II, VII, IX, and X. 

It exerts the following therapeutic effects: 

  • Prevents further extension of the formed existing clot 
  • Prevents new clot formation 
  • Prevents secondary thromboembolic complications

When given orally, warfarin has the following pharmacokinetic profile: 

  • The onset of action in 1.5 to 3 days 
  • Achieves peak in 5 to 7 days  
  • Duration of action is 2 to 5 days 
  • Well absorbed from the gastrointestinal tract 
  • The protein bounding is up to 99% 
  • It is metabolized in the liver and excreted through the kidneys  
  • Not removed by hemodialysis  
  • Has a half-life of 20 to 60 hours

What Are the Contraindications for Warfarin?

Warfarin use is contraindicated in the following cases: 

  • Hypersensitivity to warfarin 
  • Hemorrhagic tendencies such as cerebral aneurysms, bleeding from the gastrointestinal tract 
  • Recent or potential surgery of the eye or CNS 
  • Neurosurgical procedures 
  • Open wounds 
  • Severe uncontrolled or malignant hypertension  
  • Spinal puncture procedures
  • Uncontrolled bleeding
  • Ulcers
  • Unreliable or non-compliant patients
  • Unsupervised patients
  • Blood dyscrasias
  • Pericarditis or pericardial effusion
  • Pregnancy (except in women with mechanical heart valves at high risk for thromboembolism)
  • Bacterial endocarditis
  • Threatened abortion
  • Major regional lumbar block anesthesia 
  • Traumatic surgery
  • Eclampsia and preeclampsia 

In the following cases, you need to exercise caution with warfarin therapy:

  • Active tuberculosis 
  • Acute infection 
  • Diabetes 
  • Heparin-induced thrombocytopenia 
  • Deep vein thrombosis 
  • Patients at risk for hemorrhage 
  • Moderate to severe renal impairment 
  • Moderate to severe hypertension 
  • Thyroid disease 
  • Polycythemia vera 
  • Vasculitis  
  • Open wound 
  • Menstruating and postpartum women 
  • Indwelling catheters 
  • Trauma 
  • Prolonged dietary deficiencies 
  • Disruption of GI normal flora 
  • History of peptic ulcer disease 
  • Protein C deficiency 
  • Elderly 

warfarin considerations

Warfarin Black Box Warning

Warfarin has a black box warning in the following cases: 

  • Risk for major or fatal bleeding 
  • The patient has a history of GI bleeding  
  • Hypertension 
  • Cerebrovascular disease 
  • Malignancy 
  • Trauma 
  • Anemia 
  • Renal insufficiency 
  • Age 65 yrs and older 
  • High anticoagulation factor (INR greater than 4) 

When giving warfarin to the patient, check cardiac and hepatic functions, age, nutritional status, and concurrent medications, as well as assess the risk of bleeding.  

    Warfarin Drug Interactions

    Drugs that may increase the action of warfarin are: 

    • Amiodarone 
    • Azole antifungal drugs such as fluconazole  
    • Cimetidine 
    • Disulfiram 
    • Sulfamethoxazole-trimethoprim 
    • Levothyroxine 
    • Metronidazole 
    • NSAIDs, such as ibuprofen, ketorolac, naproxen  
    • Omeprazole 
    • Platelet aggregation inhibitors such as clopidogrel 
    • Salicylates such as aspirin 
    • Thrombolytic agents such as alteplase 
    • Thyroid hormones such as levothyroxine

    Drugs that may decrease the effect of warfarin are: 

    • CYP3A inducers such as carbamazepine, phenytoin, and rifampin 
    • Nafcillin 
    • Oral contraceptives 
    • Sucralfate  
    • Vitamin K  

    Warfarin Nursing Considerations

    As a nurse, you must follow these points with warfarin therapy:

    Baseline Assessment

    • Cross-check the dose with a co-worker. Ask them if you are giving the appropriate dose to the patient or not.  
    • Before administration, obtain PT and INR values of the patient and daily following therapy initiation. However, when the patient is stable, obtain INR after every 4 to 6 weeks.  
    • Screen the patient for any major active bleeding or any history of it.  
    • Take the history for the recent history of bleeding, recent trauma, surgical procedures, and epidural anesthesia. 

    Intervention and Evaluation

    • Keep an eye on the patient’s INR. 
    • Order a complete blood count to check for anemia.  
    • Check urine and stool for occult blood. 
    • Ask the patient for abdominal or back pain, severe headache, confusion, seizures, hemiparesis, and aphasia because they indicate hemorrhage. Ask them to inform you soon if they have any of these symptoms. 
    • Monitor the patient’s blood pressure and pulse rate, as low blood pressure and high pulse rate indicate hemorrhage.  
    • Question the women for the increase in the amount of menstrual discharge.  
    • Assess the patient for peripheral pulses and skin for ecchymoses and petechiae.  
    • Check the patient for excessive bleeding from minor cuts and scratches. Assess their gums for erythema and gingival bleeding. 


    The Bottom Line

    In conclusion, warfarin is a powerful and widely prescribed anticoagulant medication that plays a critical role in the prevention and treatment of various thromboembolic conditions. As a nurse, it is imperative to have a thorough understanding of warfarin’s indications, pharmacokinetics, contraindications, and potential drug interactions to ensure safe and effective administration.

    By following essential nursing considerations, such as monitoring INR values, assessing for signs of bleeding, and educating patients on the importance of regular follow-ups, you can help to optimize patient outcomes and minimize the risks associated with warfarin therapy. Through vigilance and attention to detail, nurses can play a vital role in supporting patients on their journey towards better health with warfarin treatment.

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