Drug interactions
Fosphenytoin + Prednisone
Severity: Moderate
Fosphenytoin and Prednisone: moderate 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, the active form of fosphenytoin, induces enzymes that metabolize corticosteroids and can lower prednisolone exposure, reducing the steroid effect. Phenytoin levels may also be altered by corticosteroids.
What this interaction means in plain words
Fosphenytoin and Prednisone can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fosphenytoin belongs to Central Nervous System; Prednisone belongs to Endocrine.
Why it happens
Phenytoin induces CYP3A4 and other hepatic enzymes, increasing prednisolone clearance.
What to do
Monitor clinical response to prednisone and increase the dose if needed. Monitor phenytoin concentrations when starting or stopping steroids.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Prednisone
- Bcg vaccine live + Prednisone Contraindicated
- Measles vaccine + Prednisone Contraindicated
- Mifepristone + Prednisone Contraindicated
- Prednisone + Radium-223 dichloride Contraindicated
- Prednisone + Smallpox vaccine live Contraindicated
- Adenovirus types 4 and 7 live + Prednisone Major
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 Prednisone?
MediHelp rates the interaction as moderate. Fosphenytoin and Prednisone can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenytoin, the active form of fosphenytoin, induces enzymes that metabolize corticosteroids and can lower prednisolone exposure, reducing the steroid effect. Phenytoin levels may also be altered by corticosteroids.
How serious is the interaction between Fosphenytoin and Prednisone?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor clinical response to prednisone and increase the dose if needed. Monitor phenytoin concentrations when starting or stopping steroids.
What other medicines interact with Prednisone?
MediHelp also lists interactions of Prednisone with, for example, Bcg vaccine live, Measles vaccine, Mifepristone. The full list is on the Prednisone page.
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