Warfarin with Grazoprevir Interaction Details
Brand Names Associated with Warfarin
- Coumadin®
- Jantoven®
- Warfarin
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 07, 2023
Interaction Effect
Fluctuations in INR
Interaction Summary
Concomitant use of direct-acting antivirals (with or without ribavirin) for treatment for hepatitis C virus infection (HCV) with warfarin may lead to fluctuations in INR values. In a cohort study, warfarin dose-response significantly decreased resulting in a greater than 2-fold increase in subtherapeutic INR values when any of several different combination HCV regimens were added to stable warfarin therapy. Use of ribavirin resulted in additional decrease of the dose response . Frequent monitoring of INR during and following HCV treatment is recommended .
Severity
Major
Onset
Unspecified
Evidence
Theoretical
How To Manage Interaction
Concomitant use of direct-acting antivirals (with or without ribavirin) for treatment for hepatitis C virus infection (HCV) with warfarin may lead to fluctuations in INR values. Frequent monitoring of INR during and following HCV treatment is recommended.
Mechanism Of Interaction
Unknown
Literature Reports
A) Warfarin dose-response as measured by the warfarin sensitivity index (WSI; steady state INR divided by average daily warfarin dose) was significantly decreased by 23% in patients who were on stable warfarin therapy and received one of several different direct-acting antiviral regimens (with or without ribavirin) for treatment of hepatitis C virus (HCV) infection in a cohort study (N=271). The overall WSI decreased from 0.53 to 0.39 over the 12-week course of HCV therapy. Significant decreases in WSI compared with baseline were observed for combination sofosbuvir/ledipasvir (15.1%), combination sofosbuvir/simeprevir (12.2%), and combination ombitasvir, paritaprevir, ritonavir, and dasabuvir (32%). The decrease with sofosbuvir monotherapy was nonsignificant (9.4%). Concomitant ribavirin resulted in an additional significant decrease of 16.9% in the WSI. The largest effect (49%) was observed with combination ombitasvir, paritaprevir, ritonavir, and dasabuvir plus ribavirin. Subtherapeutic INR values occurred in 26% of patients evaluated for 12 weeks prior to the study and in 58% during the 12 weeks of HCV treatment. The mean weekly warfarin dose increased from 39.9 mg at the initiation of HCV treatment to a mean 46 mg at the end of HCV therapy .
Warfarin Overview
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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.
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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.