Warfarin with Torsemide Interaction Details
Brand Names Associated with Warfarin
- Coumadin®
- Jantoven®
- Warfarin
Brand Names Associated with Torsemide
- Demadex®
- Torsemide
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 07, 2023
Interaction Effect
Increased warfarin plasma concentrations, decreased warfarin clearance, and elevated INR
Interaction Summary
Use caution with the coadministration of torsemide and warfarin as this led to an increase in INR as described in a case report. The mechanism of this interaction is theorized to be either competitive inhibition of the CYP2C9-mediated warfarin metabolism and/or the displacement of warfarin from protein binding sites by torsemide.. Increased INR monitoring is recommended when torsemide therapy is required concurrently with warfarin therapy. Additionally, if torsemide therapy is discontinued, consider increased INR monitoring to prevent a sub-therapeutic INR and adjust the warfarin dose appropriately.
Severity
Major
Onset
Delayed
Evidence
Probable
How To Manage Interaction
A case report showed an increased INR following the concomitant use of torsemide and warfarin. Therefore, practitioners should consider monitoring INR more frequently if torsemide therapy is initiated or adjusted in a patient stabilized on warfarin. Additionally, if a patient discontinues torsemide while concomitantly on warfarin, consider frequent INR monitoring and adjust the warfarin dose as needed.
Mechanism Of Interaction
Competitive inhibition of CYP2C9-mediated warfarin metabolism and/or displacement of warfarin by torsemide from protein binding sites
Literature Reports
A) A case report described elevated INR values in a 43-year-old Hispanic woman following coadministration of torsemide and warfarin. The patient, who was stabilized on warfarin, had a history of congestive heart failure, hypertension, hypothyroidism, and anemia. Concurrent medications included furosemide 40 mg/day, digoxin, carvedilol, spironolactone, lisinopril, aspirin, and levothyroxine. Over the prior 10 months, her warfarin therapy ranged from 47.5 to 52.5 mg/week and INR values ranged from 1.2 to 5.3. On June 1, she presented for an office visit with an INR of 3.1, a warfarin dose of 52.5 mg/week (7.5 mg/day), and reported a new prescription for torsemide (40 mg in the morning and 20 mg in the afternoon) to replace her furosemide 40 mg/day due to abdominal swelling and fatigue over the previous 72 hours. On June 8, she reported back with an INR of 6.2 and claimed adhering to all medications, including her transfer from furosemide to torsemide during the previous week. Subsequently, she was directed to withhold one warfarin dose, take 5-mg warfarin doses for the next 2 days, and return for a reevaluation. Three days later, her INR was 5.2 and she was instructed to again withhold one warfarin dose and take 5-mg warfarin doses for the next 3 days. Upon her return 4 days later, she had an INR of 1.8. With subsequent warfarin dose titration, therapeutic INR values of 3.3, 3.2, 3.1, 2.9 were achieved with a weekly warfarin dose of 47.5 mg .
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.
Torsemide Overview
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Torsemide is used alone or in combination with other medications to treat high blood pressure. Torsemide is used to treat edema (fluid retention; excess fluid held in body tissues) caused by various medical problems, including heart, kidney, or liver disease. Torsemide is in a class of medications called diuretics ('water pills'). It works by causing the kidneys to get rid of unneeded water and salt from the body into the urine.
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High blood pressure is a common condition, and when not treated it can cause damage to the brain, heart, blood vessels, kidneys and other parts of the body. Damage to these organs may cause heart disease, a heart attack, heart failure, stroke, kidney failure, loss of vision, and other problems. In addition to taking medication, making lifestyle changes will also help to control your blood pressure. These changes include eating a diet that is low in fat and salt, maintaining a healthy weight, exercising at least 30 minutes most days, not smoking, and using alcohol in moderation.
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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.