Drug interactions
Apalutamide + Phenytoin
Severity: Major
Apalutamide 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
Apalutamide induces CYP2C19 and CYP3A4 and may lower phenytoin concentrations, risking loss of seizure control. Phenytoin has a narrow therapeutic index, and its levels may also change unpredictably because of its nonlinear kinetics. Phenytoin, as a strong inducer itself, may also reduce apalutamide exposure.
What this interaction means in plain words
Apalutamide 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.
Apalutamide belongs to Endocrine; Phenytoin belongs to Central Nervous System.
Why it happens
Apalutamide induces CYP2C19 and CYP2C9 and increases phenytoin metabolism.
What to do
Avoid if possible or choose an alternative anticonvulsant. If combined, monitor phenytoin serum levels and seizure control and adjust the dose.
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 Apalutamide
- Apalutamide + Cabotegravir Contraindicated
- Apalutamide + Cobicistat Contraindicated
- Apalutamide + Doravirine Contraindicated
- Apalutamide + Elbasvir / grazoprevir Contraindicated
- Apalutamide + Ensitrelvir Contraindicated
- Apalutamide + Fostemsavir Contraindicated
Frequently asked questions
Can I take Apalutamide with Phenytoin?
MediHelp rates the interaction as major. Apalutamide 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. Apalutamide induces CYP2C19 and CYP3A4 and may lower phenytoin concentrations, risking loss of seizure control. Phenytoin has a narrow therapeutic index, and its levels may also change unpredictably because of its nonlinear kinetics. Phenytoin, as a strong inducer itself, may also reduce apalutamide exposure.
How serious is the interaction between Apalutamide 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 if possible or choose an alternative anticonvulsant. If combined, monitor phenytoin serum levels and seizure control and adjust the dose.
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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