Drug interactions
Armodafinil + Phenytoin
Severity: Moderate
Armodafinil 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 a CYP3A4 inducer and can lower armodafinil exposure, possibly reducing its wakefulness effect. Armodafinil may also inhibit CYP2C19, which could raise phenytoin levels in some patients.
What this interaction means in plain words
Armodafinil 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.
Armodafinil belongs to Central Nervous System; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and increases armodafinil clearance, while armodafinil may inhibit CYP2C19-mediated phenytoin metabolism.
What to do
Monitor phenytoin serum concentrations and signs of toxicity such as nystagmus or ataxia when armodafinil is started or stopped. Consider a higher armodafinil dose if efficacy is lost.
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 Armodafinil
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 Armodafinil with Phenytoin?
MediHelp rates the interaction as moderate. Armodafinil 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 a CYP3A4 inducer and can lower armodafinil exposure, possibly reducing its wakefulness effect. Armodafinil may also inhibit CYP2C19, which could raise phenytoin levels in some patients.
How serious is the interaction between Armodafinil 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 phenytoin serum concentrations and signs of toxicity such as nystagmus or ataxia when armodafinil is started or stopped. Consider a higher armodafinil dose if efficacy is lost.
What other medicines interact with Armodafinil?
MediHelp also lists interactions of Armodafinil with, for example, Avapritinib, Elacestrant, Elbasvir / grazoprevir. The full list is on the Armodafinil page.
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