Drug interactions
Leflunomide + Mercaptopurine
Severity: Major
Leflunomide and Mercaptopurine: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Both drugs can cause myelosuppression and hepatotoxicity, and together they add to immunosuppression. The risk of pancytopenia, liver injury and serious infection is increased.
What this interaction means in plain words
Leflunomide and Mercaptopurine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Leflunomide belongs to Musculoskeletal; Mercaptopurine belongs to Oncology.
Why it happens
Additive immunosuppression, bone marrow suppression and hepatotoxicity via inhibition of pyrimidine synthesis and purine metabolism.
What to do
Avoid the combination if possible; if used, monitor complete blood counts and liver enzymes every few weeks initially. Stop and consider leflunomide washout if serious toxicity occurs.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Mercaptopurine
- Adenovirus types 4 and 7 live + Mercaptopurine Contraindicated
- Azathioprine + Mercaptopurine Contraindicated
- Bcg vaccine live + Mercaptopurine Contraindicated
- Febuxostat + Mercaptopurine Contraindicated
- Influenza virus vaccine quadrivalent intranasal + Mercaptopurine Contraindicated
- Mercaptopurine + Smallpox vaccine live Contraindicated
Other interactions of Leflunomide
- Bcg vaccine live + Leflunomide Contraindicated
- Influenza virus vaccine quadrivalent intranasal + Leflunomide Contraindicated
- Leflunomide + Measles mumps and rubella vaccine live Contraindicated
- Leflunomide + Measles mumps rubella and varicella vaccine live Contraindicated
- Leflunomide + Measles vaccine Contraindicated
- Leflunomide + Smallpox vaccine live Contraindicated
Frequently asked questions
Can I take Leflunomide with Mercaptopurine?
MediHelp rates the interaction as major. Leflunomide and Mercaptopurine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Both drugs can cause myelosuppression and hepatotoxicity, and together they add to immunosuppression. The risk of pancytopenia, liver injury and serious infection is increased.
How serious is the interaction between Leflunomide and Mercaptopurine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination if possible; if used, monitor complete blood counts and liver enzymes every few weeks initially. Stop and consider leflunomide washout if serious toxicity occurs.
What other medicines interact with Mercaptopurine?
MediHelp also lists interactions of Mercaptopurine with, for example, Adenovirus types 4 and 7 live, Azathioprine, Bcg vaccine live. The full list is on the Mercaptopurine page.
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