Drug interactions
Isavuconazole + Phenytoin
Severity: Contraindicated
Isavuconazole and Phenytoin: contraindicated 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 is an enzyme inducer that reduces isavuconazole exposure, risking loss of antifungal efficacy. Isavuconazole may also modestly raise phenytoin levels.
What this interaction means in plain words
Isavuconazole and Phenytoin are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Isavuconazole belongs to Anti Fungals; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4/5, increasing isavuconazole metabolism.
What to do
Avoid the combination and use a non-inducing anticonvulsant such as levetiracetam, or another antifungal. If it cannot be avoided, monitor isavuconazole and phenytoin concentrations closely.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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Other interactions of Isavuconazole
- Carbamazepine + Isavuconazole Contraindicated
- Efavirenz + Isavuconazole Contraindicated
- Etravirine + Isavuconazole Contraindicated
- Isavuconazole + Ketoconazole Contraindicated
- Isavuconazole + Phenobarbitone Contraindicated
- Isavuconazole + Rifampicin Contraindicated
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 Isavuconazole with Phenytoin?
MediHelp rates the interaction as contraindicated. Isavuconazole and Phenytoin are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Phenytoin is an enzyme inducer that reduces isavuconazole exposure, risking loss of antifungal efficacy. Isavuconazole may also modestly raise phenytoin levels.
How serious is the interaction between Isavuconazole and Phenytoin?
MediHelp rates it contraindicated, 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 anticonvulsant such as levetiracetam, or another antifungal. If it cannot be avoided, monitor isavuconazole and phenytoin concentrations closely.
What other medicines interact with Isavuconazole?
MediHelp also lists interactions of Isavuconazole with, for example, Carbamazepine, Efavirenz, Etravirine. The full list is on the Isavuconazole page.
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