Warfarin with Menatetrenone Interaction Details
Brand Names Associated with Warfarin
- Coumadin®
- Jantoven®
- Warfarin
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 07, 2023
Interaction Effect
A change in or fluctuation of INR
Interaction Summary
Vitamin K is found in enteral nutritional products, dietary supplements, herbal products, and is commonly added to hyperalimentation solutions. These sources of vitamin K can interfere with warfarin's anticoagulant effects, which are based upon inhibition of the activation of vitamin K-dependent clotting factors. If coadministered, increase INR monitoring .
Severity
Moderate
Onset
Delayed
Evidence
Probable
How To Manage Interaction
Vitamin K-containing products will competitively antagonize the metabolism or warfarin and should not be used in patients receiving oral anticoagulant therapy except in cases of acute bleeding due to excessive anticoagulation. If coadministered, increase INR monitoring .
Mechanism Of Interaction
Antagonism of warfarin's mechanism of action
Literature Reports
A) The S-warfarin enantiomer is affected by vitamin K to a greater extent than the R-warfarin enantiomer. Following phytonadione administration, the area under the plasma concentration-time curve for the metabolite vitamin K (1) 2,3-epoxide was greater after S-warfarin than after R-warfarin .
B) Dietary vitamin K in amounts greater than or equal to 250 mcg daily led to reduced response to warfarin in 32% of patients. Patients (n=50) tracked vitamin K intake for 8 weeks. The range of vitamin K intake was from 17 to 974 mcg daily. Warfarin sensitivity (warfarin sensitivity index (WSI)) was defined as the final international normalization ratio (INR)/final warfarin daily dose measured in mg/m(2) after week 8. The median WSI was 0.82. A WSI value of 1.1 significantly separated excess (greater than 250 mcg daily) from normal (under 250 mcg daily) ingestion of vitamin K. Patients with large dietary intake of vitamin K had significantly lower day 5 INR (1.9 vs 3). They also required additional warfarin to produce an INR greater than 2 and required more warfarin to maintain a steady state INR, both of these findings were significant .
C) Warfarin doses required to reach and maintain a target INR were larger in a group of children given enteral feedings with supplemented vitamin K (n=82) than in a group not fed the supplemented formula (n=270). The differences between the two groups were significant for: (1) the dose required to reach target INR, (2) doses required to maintain INR, and (3) the number of days of overlap of warfarin and heparin .
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.