Warfarin with Cefazolin Interaction Details


Brand Names Associated with Warfarin

  • Coumadin®
  • Jantoven®
  • Warfarin

Brand Names Associated with Cefazolin

  • Ancef®
  • Cefazolin Injection
  • Kefzol®

Medical Content Editor
Last updated Nov 07, 2023


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Interaction Effect

An increased risk of bleeding


Interaction Summary

Case reports and one study indicate that cefazolin may produce hypoprothrombinemia and may enhance the anticoagulant effect of warfarin.


Severity

Moderate


Onset

Delayed


Evidence

Probable


How To Manage Interaction

Patients receiving oral anticoagulant therapy with warfarin should be closely monitored using the prothrombin time ratio or international normalized ratio (INR) during concurrent therapy with cefazolin. Adjustment of the warfarin dosage to maintain the desired anticoagulant effect may be necessary. An alternative would be to use a cephalosporin which does not possess hypoprothrombinemic properties.


Mechanism Of Interaction

Decreased synthesis of vitamin K-dependent clotting factors


Literature Reports

A) The effects of cefamandole, cefazolin, and vancomycin on the prothrombin response to warfarin were evaluated in patients receiving these antibiotics as prophylaxis for prosthetic valve surgery. Cefamandole was demonstrated to produce additive hypoprothrombinemic effects with warfarin, with these effects being greater than those observed with cefazolin and vancomycin; cefazolin appeared to be intermediate between cefamandole and vancomycin with regard to producing additive hypoprothrombinemia. Significantly greater percentage changes in prothrombin were observed with cefamandole (64%) from the first to the third day of anticoagulation as compared to cefazolin (51%) or vancomycin (45%). These data suggest that the influence on prothrombin response to warfarin is ranked as cefamandole greater than cefazolin greater than vancomycin .

Warfarin Overview

  • Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic (replacement or mechanical) heart valves, and people who have suffered a heart attack. Warfarin is also used to treat or prevent venous thrombosis (swelling and blood clot in a vein) and pulmonary embolism (a blood clot in the lung). Warfarin is in a class of medications called anticoagulants ('blood thinners'). It works by decreasing the clotting ability of the blood.

See More information Regarding Warfarin

Cefazolin Overview

  • Cefazolin injection is used to treat certain infections caused by bacteria including skin, bone, joint, genital, blood, heart valve, respiratory tract (including pneumonia), biliary tract, and urinary tract infections. Cefazolin injection also may be used before, during, and sometimes for a brief period after surgery in order to prevent the patient from getting an infection. Cefazolin injection is in a class of medications called cephalosporin antibiotics. It works by killing bacteria.

  • Antibiotics such as cefazolin injection will not work for colds, flu, or other viral infections. Taking antibiotics when they are not needed increases your risk of getting an infection later that resists antibiotic treatment.

See More information Regarding Cefazolin Injection

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Definitions

Severity Categories

Contraindicated

These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.


Major

This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.


Moderate

This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.


Minor

While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.


Onset

Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.

Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.


Evidence

Level of documentation of the interaction.

Established: The interaction is documented and substantiated in peer-reviewed medical literature.

Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.


How To Manage The Interaction

Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.

It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.


Mechanism Of Interaction

The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.


Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.

Where Does Our Information Come From?

Information for our drug interactions is compiled from several drug compendia, including:

The prescribing information for each drug, as published on DailyMED, is also used. 

Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.

The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.