Mercaptopurine with Balsalazide Interaction Details
Brand Names Associated with Mercaptopurine
- 6-MP
- Mercaptopurine
- Purinethol®
- Purixan®
Brand Names Associated with Balsalazide
- Balsalazide
- Colazal®
- Giazo®

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Dec 29, 2023
Interaction Effect
An increased risk of myelosuppression
Interaction Summary
6-mercaptopurine is metabolized by thiopurine methyltransferase (TPMT), an enzyme which converts the drug to 6-methylmercaptopurine. Decreased TPMT activity causes increased active metabolites of 6-mercaptopurine to accumulate, which has been associated with an increased risk of life-threatening myelosuppression. Balsalazide is a relatively potent inhibitor of TPMT activity. Therefore, careful monitoring of blood counts is recommended in patients receiving concomitant therapy with 6-mercaptopurine and balsalazide.
Severity
Moderate
Onset
Delayed
Evidence
Theoretical
How To Manage Interaction
Caution should be exercised when coprescribing balsalazide and 6-mercaptopurine. Complete blood counts should be closely monitored.
Mechanism Of Interaction
Inhibition by balsalazide of thiopurine methyltransferase
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.
Balsalazide Overview
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Balsalazide is used to treat ulcerative colitis (a condition which causes swelling and sores in the lining of the colon [large intestine] and rectum) in adults and children 5 years of age and older. Balsalazide is an anti-inflammatory drug. It is converted in the body to mesalamine and works by reducing bowel inflammation, diarrhea, rectal bleeding, and stomach pain.
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This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.
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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.