Drug interactions
Aprepitant + Fosphenytoin
Severity: Moderate
Aprepitant and Fosphenytoin: 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, the active form of fosphenytoin, induces CYP3A4 and can substantially reduce aprepitant concentrations. This may result in loss of antiemetic efficacy. Aprepitant may also alter phenytoin levels through CYP2C9 induction.
What this interaction means in plain words
Aprepitant and Fosphenytoin 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.
Aprepitant belongs to Gastrointestinal Tract; Fosphenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and increases aprepitant clearance.
What to do
Monitor for breakthrough nausea and vomiting and consider additional antiemetics. Check phenytoin levels when aprepitant is started or stopped.
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 Aprepitant
- Aprepitant + Lomitapide Contraindicated
- Aprepitant + Pimozide Contraindicated
- Aprepitant + Avapritinib Major
- Aprepitant + Bosutinib Major
- Aprepitant + Carbamazepine Major
- Aprepitant + Cobicistat Major
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Aprepitant with Fosphenytoin?
MediHelp rates the interaction as moderate. Aprepitant and Fosphenytoin 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, the active form of fosphenytoin, induces CYP3A4 and can substantially reduce aprepitant concentrations. This may result in loss of antiemetic efficacy. Aprepitant may also alter phenytoin levels through CYP2C9 induction.
How serious is the interaction between Aprepitant and Fosphenytoin?
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 for breakthrough nausea and vomiting and consider additional antiemetics. Check phenytoin levels when aprepitant is started or stopped.
What other medicines interact with Aprepitant?
MediHelp also lists interactions of Aprepitant with, for example, Lomitapide, Pimozide, Avapritinib. The full list is on the Aprepitant page.
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