Drug interactions
Phenytoin + Tasimelteon
Severity: Moderate
Phenytoin and Tasimelteon: 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 may considerably lower tasimelteon exposure, reducing its effect on non-24-hour sleep-wake disorder.
What this interaction means in plain words
Phenytoin and Tasimelteon 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; Tasimelteon belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, increasing tasimelteon clearance.
What to do
Avoid combining with strong CYP3A4 inducers where possible, and monitor for loss of efficacy if concurrent use is 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?
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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 Tasimelteon
Frequently asked questions
Can I take Phenytoin with Tasimelteon?
MediHelp rates the interaction as moderate. Phenytoin and Tasimelteon 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 may considerably lower tasimelteon exposure, reducing its effect on non-24-hour sleep-wake disorder.
How serious is the interaction between Phenytoin and Tasimelteon?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid combining with strong CYP3A4 inducers where possible, and monitor for loss of efficacy if concurrent use is needed.
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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