Drug interactions
Ivosidenib + Phenytoin
Severity: Major
Ivosidenib and Phenytoin: major interaction.
Last updated Sources: EMA 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 may lower ivosidenib exposure through CYP3A4 induction, risking reduced efficacy. Ivosidenib may in turn alter phenytoin levels, as it affects CYP2C9 and other enzymes, making the net effect unpredictable for a narrow therapeutic index drug.
What this interaction means in plain words
Ivosidenib 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.
Ivosidenib belongs to Oncology; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 to increase ivosidenib clearance, while ivosidenib modulates CYP2C9 involved in phenytoin metabolism.
What to do
Avoid the combination and use a non-inducing antiseizure drug. If unavoidable, monitor phenytoin serum levels and the response to ivosidenib.
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 Ivosidenib
- Alfuzosin + Ivosidenib Major
- Amiodarone + Ivosidenib Major
- Amisulpride + Ivosidenib Major
- Amitriptyline + Ivosidenib Major
- Amobarbital + Ivosidenib Major
- Anagrelide + Ivosidenib Major
Frequently asked questions
Can I take Ivosidenib with Phenytoin?
MediHelp rates the interaction as major. Ivosidenib 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 may lower ivosidenib exposure through CYP3A4 induction, risking reduced efficacy. Ivosidenib may in turn alter phenytoin levels, as it affects CYP2C9 and other enzymes, making the net effect unpredictable for a narrow therapeutic index drug.
How serious is the interaction between Ivosidenib 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 use a non-inducing antiseizure drug. If unavoidable, monitor phenytoin serum levels and the response to ivosidenib.
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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