Drug interactions
Phenytoin + Tofacitinib
Severity: Moderate
Phenytoin and Tofacitinib: 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 a strong inducer of CYP3A4 and can lower tofacitinib exposure considerably. This may lead to loss of therapeutic effect in rheumatoid arthritis, psoriatic arthritis or ulcerative colitis.
What this interaction means in plain words
Phenytoin and Tofacitinib 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 belongs to Central Nervous System; Tofacitinib belongs to Musculoskeletal.
Why it happens
Phenytoin induces CYP3A4, the main metabolic pathway of tofacitinib, increasing its clearance.
What to do
Monitor clinical response to tofacitinib and consider an alternative anticonvulsant or alternative therapy if efficacy is lost. Tofacitinib labeling advises against relying on dose escalation to overcome induction.
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?
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Other interactions of Tofacitinib
- Baricitinib + Tofacitinib Contraindicated
- Cladribine + Tofacitinib Contraindicated
- Tofacitinib + Upadacitinib Contraindicated
- Abatacept + Tofacitinib Major
- Anti-thymocyte + Tofacitinib Major
- Antithymocyte globulin equine + Tofacitinib Major
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 Phenytoin with Tofacitinib?
MediHelp rates the interaction as moderate. Phenytoin and Tofacitinib 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 a strong inducer of CYP3A4 and can lower tofacitinib exposure considerably. This may lead to loss of therapeutic effect in rheumatoid arthritis, psoriatic arthritis or ulcerative colitis.
How serious is the interaction between Phenytoin and Tofacitinib?
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 clinical response to tofacitinib and consider an alternative anticonvulsant or alternative therapy if efficacy is lost. Tofacitinib labeling advises against relying on dose escalation to overcome induction.
What other medicines interact with Tofacitinib?
MediHelp also lists interactions of Tofacitinib with, for example, Baricitinib, Cladribine, Upadacitinib. The full list is on the Tofacitinib page.
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