Drug interactions
Fosphenytoin + Regorafenib
Severity: Major
Fosphenytoin and Regorafenib: 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, the active form of fosphenytoin, induces CYP3A4 and may lower regorafenib exposure, risking reduced efficacy.
What this interaction means in plain words
Fosphenytoin and Regorafenib 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.
Fosphenytoin belongs to Central Nervous System; Regorafenib belongs to Oncology.
Why it happens
Phenytoin induces CYP3A4, accelerating regorafenib metabolism.
What to do
Avoid strong CYP3A4 inducers; use a non-inducing anticonvulsant such as levetiracetam when possible.
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 Regorafenib
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 Fosphenytoin with Regorafenib?
MediHelp rates the interaction as major. Fosphenytoin and Regorafenib 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 regorafenib exposure, risking reduced efficacy.
How serious is the interaction between Fosphenytoin and Regorafenib?
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; use a non-inducing anticonvulsant such as levetiracetam when possible.
What other medicines interact with Regorafenib?
MediHelp also lists interactions of Regorafenib with, for example, Apalutamide, Atazanavir, Carbamazepine. The full list is on the Regorafenib page.
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