Drug interactions
Irinotecan liposomal + Phenytoin
Severity: Major
Irinotecan liposomal and Phenytoin: major interaction.
Last updated Sources: US FDA label
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 and other enzyme-inducing antiseizure drugs substantially lower exposure to irinotecan's active metabolite SN-38. This may reduce antitumor efficacy of liposomal irinotecan.
What this interaction means in plain words
Irinotecan liposomal 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.
Why it happens
Phenytoin induces CYP3A4 and UGT1A1, increasing irinotecan oxidation and SN-38 glucuronidation.
What to do
Avoid strong CYP3A4 inducers and substitute a non-inducing antiseizure drug if possible. Monitor tumor response and neutropenia if combination is unavoidable.
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
Frequently asked questions
Can I take Irinotecan liposomal with Phenytoin?
MediHelp rates the interaction as major. Irinotecan liposomal 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 and other enzyme-inducing antiseizure drugs substantially lower exposure to irinotecan's active metabolite SN-38. This may reduce antitumor efficacy of liposomal irinotecan.
How serious is the interaction between Irinotecan liposomal 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 CYP3A4 inducers and substitute a non-inducing antiseizure drug if possible. Monitor tumor response and neutropenia if combination is unavoidable.
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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