Drug interactions
Ensitrelvir + Phenytoin
Severity: Contraindicated
Ensitrelvir and Phenytoin: contraindicated 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 expected to lower ensitrelvir exposure significantly, risking inadequate antiviral effect. Labeling contraindicates strong CYP3A inducers with ensitrelvir.
What this interaction means in plain words
Ensitrelvir and Phenytoin are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Ensitrelvir belongs to Anti Virals; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, increasing ensitrelvir clearance.
What to do
Avoid coadministration and use an alternative COVID-19 antiviral not affected by induction. Use a non-inducing anticonvulsant if the patient's seizure management allows.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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Other interactions of Ensitrelvir
- Apalutamide + Ensitrelvir Contraindicated
- Carbamazepine + Ensitrelvir Contraindicated
- Colchicine + Ensitrelvir Contraindicated
- Ensitrelvir + Enzalutamide Contraindicated
- Ensitrelvir + Eplerenone Contraindicated
- Ensitrelvir + Finerenone 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 Ensitrelvir with Phenytoin?
MediHelp rates the interaction as contraindicated. Ensitrelvir and Phenytoin are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Phenytoin is expected to lower ensitrelvir exposure significantly, risking inadequate antiviral effect. Labeling contraindicates strong CYP3A inducers with ensitrelvir.
How serious is the interaction between Ensitrelvir and Phenytoin?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid coadministration and use an alternative COVID-19 antiviral not affected by induction. Use a non-inducing anticonvulsant if the patient's seizure management allows.
What other medicines interact with Ensitrelvir?
MediHelp also lists interactions of Ensitrelvir with, for example, Apalutamide, Carbamazepine, Colchicine. The full list is on the Ensitrelvir page.
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