Drug interactions
Entrectinib + Phenytoin
Severity: Major
Entrectinib and Phenytoin: major interaction.
Last updated Sources: UK SmPC
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 reduces entrectinib exposure, which may impair control of tumors including CNS metastases.
What this interaction means in plain words
Entrectinib and Phenytoin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Entrectinib belongs to Oncology; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, increasing entrectinib clearance.
What to do
Avoid the combination and switch to a non-inducing antiepileptic.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
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 Entrectinib
Frequently asked questions
Can I take Entrectinib with Phenytoin?
MediHelp rates the interaction as major. Entrectinib and Phenytoin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Phenytoin reduces entrectinib exposure, which may impair control of tumors including CNS metastases.
How serious is the interaction between Entrectinib and Phenytoin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination and switch to a non-inducing antiepileptic.
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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