Drug interactions
Crizotinib + Phenytoin
Severity: Major
Crizotinib 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, a strong CYP3A inducer, can markedly lower crizotinib exposure and reduce antitumor efficacy. Crizotinib is also a CYP3A inhibitor and may raise levels of narrow therapeutic index CYP3A substrates, though phenytoin is mainly cleared by CYP2C9 and 2C19.
What this interaction means in plain words
Crizotinib 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.
Crizotinib belongs to Oncology; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, increasing crizotinib clearance; crizotinib inhibits CYP3A4 and may modestly affect phenytoin.
What to do
Avoid strong CYP3A inducers with crizotinib and choose a non-inducing antiseizure drug such as levetiracetam. If unavoidable, monitor tumor response and phenytoin levels closely.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Crizotinib and Phenytoin, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
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 Crizotinib
- Crizotinib + Flibanserin Contraindicated
- Crizotinib + Lomitapide Contraindicated
- Crizotinib + Lonafarnib Contraindicated
- Crizotinib + Pimozide Contraindicated
- Crizotinib + Saquinavir Contraindicated
- Crizotinib + Thioridazine Contraindicated
Frequently asked questions
Can I take Crizotinib with Phenytoin?
MediHelp rates the interaction as major. Crizotinib 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, a strong CYP3A inducer, can markedly lower crizotinib exposure and reduce antitumor efficacy. Crizotinib is also a CYP3A inhibitor and may raise levels of narrow therapeutic index CYP3A substrates, though phenytoin is mainly cleared by CYP2C9 and 2C19.
How serious is the interaction between Crizotinib 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 strong CYP3A inducers with crizotinib and choose a non-inducing antiseizure drug such as levetiracetam. If unavoidable, monitor tumor response and phenytoin levels closely.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
