Drug interactions
Enzalutamide + Fosphenytoin
Severity: Major
Enzalutamide and Fosphenytoin: 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, the active form of fosphenytoin, induces CYP3A4 and may lower enzalutamide exposure, reducing its efficacy. Enzalutamide may in turn alter phenytoin levels.
What this interaction means in plain words
Enzalutamide and Fosphenytoin 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.
Enzalutamide belongs to Endocrine; Fosphenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, increasing enzalutamide and active metabolite clearance.
What to do
Avoid the combination and use a non-inducing anticonvulsant such as levetiracetam. If unavoidable, monitor phenytoin levels and consider enzalutamide dose adjustment.
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 Enzalutamide
- Doravirine + Enzalutamide Contraindicated
- Elbasvir / grazoprevir + Enzalutamide Contraindicated
- Ensitrelvir + Enzalutamide Contraindicated
- Enzalutamide + Fostemsavir Contraindicated
- Enzalutamide + Isavuconazonium Contraindicated
- Enzalutamide + Lenacapavir Contraindicated
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Enzalutamide with Fosphenytoin?
MediHelp rates the interaction as major. Enzalutamide and Fosphenytoin 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, the active form of fosphenytoin, induces CYP3A4 and may lower enzalutamide exposure, reducing its efficacy. Enzalutamide may in turn alter phenytoin levels.
How serious is the interaction between Enzalutamide and Fosphenytoin?
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 anticonvulsant such as levetiracetam. If unavoidable, monitor phenytoin levels and consider enzalutamide dose adjustment.
What other medicines interact with Enzalutamide?
MediHelp also lists interactions of Enzalutamide with, for example, Doravirine, Elbasvir / grazoprevir, Ensitrelvir. The full list is on the Enzalutamide page.
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