Warfarin with Tolterodine Interaction Details
Brand Names Associated with Warfarin
- Coumadin®
- Jantoven®
- Warfarin
Brand Names Associated with Tolterodine
- Detrol®
- Detrol® LA
- Tolterodine
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 07, 2023
Interaction Effect
An increased risk of bleeding
Interaction Summary
No pharmacokinetic or pharmacodynamic interactions were seen between warfarin and tolterodine in healthy volunteers. Dosing regimens included warfarin and placebo or warfarin and tolterodine 2 mg twice daily for seven days and a single dose of warfarin 25 mg on day 4. However, two subjects experienced a significant increase in international normalize ratio (INR) 10 to 14 days after tolterodine was introduced. Two weeks after discontinuation of tolterodine, INR levels returned to baseline, suggesting a drug interaction when tolterodine therapy is initiated in patients who are maintained on warfarin therapy .
Severity
Moderate
Onset
Delayed
Evidence
Probable
How To Manage Interaction
In patients receiving oral anticoagulant therapy with warfarin, anticoagulant response should be assessed with the prothrombin time ratio or international normalized ratio (INR) upon the addition and withdrawal of tolterodine. Warfarin dose should be adjusted accordingly to maintain the desired level of anticoagulation.
Mechanism Of Interaction
Competition for cytochrome P450 3A4-mediated metabolism
Literature Reports
A) Both a 72-year-old and an 83-year-old white male who were receiving constant doses of warfarin for stroke prophylaxis in association with chronic atrial fibrillation developed adverse effects after tolterodine was introduced. In both cases, an increase in the international normalized ratio (INR) from baselines of 1.2 and 1.8 to 6.1 and 7.4, respectively, was seen 14 days after tolterodine initiation. Two weeks after tolterodine was discontinued, INR values returned to levels similar to those prior to tolterodine initiation. Similarities in the two cases lend validity to a proposed drug interaction when tolterodine is initiated in a patient stabilized on warfarin 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.
Tolterodine Overview
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Tolterodine is used treat overactive bladder (a condition in which the bladder muscles contract uncontrollably and cause frequent urination, urgent need to urinate, and inability to control urination). Tolterodine is in a class of medications called antimuscarinics. It works by relaxing the bladder muscles preventing bladder contraction.
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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.