Warfarin with Menthol Interaction Details
Brand Names Associated with Warfarin
- Coumadin®
- Jantoven®
- Warfarin
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 07, 2023
Interaction Effect
Reduced anticoagulant effectiveness of warfarin
Interaction Summary
In 2 case reports, concomitant ingestion of menthol-containing cough drops appeared to reduce the INR to subtherapeutic range in patients receiving anticoagulation therapy with warfarin. Although the exact mechanism of this interaction is unknown, authors postulate that it could be related to menthol's possible effect on warfarin metabolism as a CYP enzyme inducer or inhibitor of certain isoenzymes. It is recommended that patients be closely monitored and advised regarding the potential for menthol-containing cough drops to interact with warfarin . In addition, monitoring the INR and periodically reassessing the coagulation parameters may be warranted during concurrent therapy. Adjustments of the warfarin dose may also be required in order to maintain the desired level of anticoagulation.
Severity
Moderate
Onset
Unspecified
Evidence
Probable
How To Manage Interaction
Concomitant ingestion of menthol-containing cough drops has been shown to reduce the INR to subtherapeutic range in 2 case reports. Therefore, patients should be closely monitored and advised of the potential for menthol-containing cough drops to interact with warfarin . Consider monitoring the INR and periodically reassessing the coagulation parameters during concurrent therapy. Consideration should also be given to warfarin dose adjustments in order to maintain the desired level of anticoagulation.
Mechanism Of Interaction
Unknown
Literature Reports
A) INR decreased to a subtherapeutic range in a 46-year-old man following concomitant use of menthol-containing cough drops and warfarin. The patient was being treated with amlodipine, enalapril, fexofenadine and fish oil for hypertension and sleep apnea. Two weeks after being initiated on warfarin 50 mg weekly for a venous thromboembolism, his INR dropped from 2.6 to 1.6 (target range, 2 to 3). Although his warfarin dose was increased over the next 3 weeks, his INR stayed at 1.6. The patient's warfarin dose and compliance all of his medications over the previous 2 weeks were verified. However, he had been taking 8 to 10 menthol-containing cough drops per day during this time. Subsequently, the cough drops were discontinued resulting in an INR increase from 1.6 to 2.9 five days later. Over the next 5 weeks, his INR was stabilized in the target range at a warfarin dose of 40 mg. The Naranjo probability scale rated the likelihood of this menthol/warfarin interaction as probable. Although the exact mechanism of this interaction is unknown, authors postulate that it could be related to menthol's possible effect on warfarin metabolism as a CYP enzyme inducer or inhibitor of certain isoenzymes .
B) Concomitant ingestion of menthol-containing cough drops appeared to reduce the INR to subtherapeutic range in a patient receiving anticoagulation therapy with warfarin. In a case report, a 57-year-old man exhibited apparently stable INR values for approximately 3 weeks after beginning warfarin therapy (attaining target range values between 2.28 and 2.68 while receiving warfarin 49 mg weekly). During the fourth week, the patient began using menthol cough drops for a flu-like illness (approximately 6 drops/day over 4 days; estimated menthol dose of 42 mg daily), during which time the INR declined to 1.45. The warfarin dose was temporarily increased to 53 mg/week, inducing an increase in INR to 2.22. The patient discontinued use of menthol cough drops; INR thereafter increased to 3.06 and the patient's dose regimen was successfully restored to the baseline dose of warfarin 49 mg weekly. The likelihood of interaction was given a Naranjo probability rating of possible .
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.