Drug interactions
Leflunomide + Phenytoin
Severity: Moderate
Leflunomide and Phenytoin: moderate 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
Phenytoin is metabolized mainly by CYP2C9, which teriflunomide inhibits. Phenytoin levels may rise, leading to nystagmus, ataxia or other toxicity given its narrow therapeutic range.
What this interaction means in plain words
Leflunomide and Phenytoin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Leflunomide belongs to Musculoskeletal; Phenytoin belongs to Central Nervous System.
Why it happens
Teriflunomide inhibits CYP2C9, reducing phenytoin clearance.
What to do
Monitor serum phenytoin concentrations and for signs of toxicity after starting leflunomide. Reduce the phenytoin dose as needed.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Leflunomide and Phenytoin, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
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
Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Frequently asked questions
Can I take Leflunomide with Phenytoin?
MediHelp rates the interaction as moderate. Leflunomide and Phenytoin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenytoin is metabolized mainly by CYP2C9, which teriflunomide inhibits. Phenytoin levels may rise, leading to nystagmus, ataxia or other toxicity given its narrow therapeutic range.
How serious is the interaction between Leflunomide and Phenytoin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor serum phenytoin concentrations and for signs of toxicity after starting leflunomide. Reduce the phenytoin dose as needed.
What other medicines interact with Leflunomide?
MediHelp also lists interactions of Leflunomide with, for example, Bcg vaccine live, Influenza virus vaccine quadrivalent intranasal, Measles mumps and rubella vaccine live. The full list is on the Leflunomide page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
