Mercaptopurine with Phenprocoumon Interaction Details
Brand Names Associated with Mercaptopurine
- 6-MP
- Mercaptopurine
- Purinethol®
- Purixan®
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Dec 29, 2023
Interaction Effect
Reduced phenprocoumon efficacy
Interaction Summary
Two patients who experienced a decrease in their international normalized ratio (INR) when azathioprine was added to phenprocoumon therapy have been described. Possible mechanisms for this interaction include induction of phenprocoumon metabolism, decreased gastrointestinal absorption of phenprocoumon, and an increase in prothrombin synthesis.
Severity
Moderate
Onset
Delayed
Evidence
Probable
How To Manage Interaction
In patients receiving oral anticoagulant therapy, the prothrombin time (PT) or international normalized ratio (INR) should be closely monitored with the addition and withdrawal of treatment with azathioprine, and should be reassessed periodically during concurrent therapy. Adjustments of the phenprocoumon dose may be necessary in order to maintain the desired level of anticoagulation.
Mechanism Of Interaction
Unknown
Literature Reports
A) Two case reports describe a decrease in phenprocoumon efficacy when azathioprine was added to therapy. Both patients had systemic lupus erythematosus (SLE). Patient 1, a 19-year-old female, received phenprocoumon as prophylaxis against thromboses. Cyclophosphamide treatment was replaced by azathioprine 100 mg daily, and the international normalized ratio (INR) decreased from 2.5 to 1.1 four weeks after azathioprine was initiated. The phenprocoumon dose was increased from an average of 2.35 mg daily to 4.5 mg daily to maintain the INR in a therapeutic range (2.0-3.0). Patient 2, a 49-year-old female, was stabilized on phenprocoumon when her cyclophosphamide treatment was also changed to azathioprine 100 mg daily. Her INR decreased from 2.4 to 1.2 during the first six weeks of concomitant therapy. The average phenprocoumon dose was increased from 3.32 mg daily to 5.79 mg daily to return the INR to 2.0 .
Mercaptopurine Overview
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Mercaptopurine is used alone or with other chemotherapy drugs to treat acute lymphocytic leukemia (ALL; also called acute lymphoblastic leukemia and acute lymphatic leukemia; a type of cancer that begins in the white blood cells). Mercaptopurine is in a class of medications called purine antagonists. It works by stopping the growth of cancer cells.
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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.