Drug interactions
Phenytoin + Ponesimod
Severity: Moderate
Phenytoin and Ponesimod: 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 enzyme inducer and may lower ponesimod exposure. This could reduce its effect on lymphocyte count and weaken disease control in multiple sclerosis. The clinical significance is not well established because it rests on limited data.
What this interaction means in plain words
Phenytoin and Ponesimod 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; Ponesimod belongs to Central Nervous System.
Why it happens
Induction of CYP3A4 and UGT1A1 by phenytoin increases the metabolic clearance of ponesimod.
What to do
Labeling advises against combining ponesimod with strong inducers of CYP3A4 and UGT1A1; choose a non-inducing anticonvulsant if possible. If the combination is unavoidable, monitor for loss of MS disease control and lymphocyte response.
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 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
Other interactions of Ponesimod
- Fingolimod + Ponesimod Contraindicated
- Ponesimod + Siponimod Contraindicated
- Amiodarone + Ponesimod Major
- Amisulpride + Ponesimod Major
- Anagrelide + Ponesimod Major
- Anti-thymocyte + Ponesimod Major
Frequently asked questions
Can I take Phenytoin with Ponesimod?
MediHelp rates the interaction as moderate. Phenytoin and Ponesimod 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 enzyme inducer and may lower ponesimod exposure. This could reduce its effect on lymphocyte count and weaken disease control in multiple sclerosis. The clinical significance is not well established because it rests on limited data.
How serious is the interaction between Phenytoin and Ponesimod?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Labeling advises against combining ponesimod with strong inducers of CYP3A4 and UGT1A1; choose a non-inducing anticonvulsant if possible. If the combination is unavoidable, monitor for loss of MS disease control and lymphocyte response.
What other medicines interact with Phenytoin?
MediHelp also lists interactions of Phenytoin with, for example, Artemether / lumefantrine, Bictegravir, Cabotegravir. The full list is on the Phenytoin page.
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