Drug interactions
Fosphenytoin + Hydrocortisone
Severity: Moderate
Fosphenytoin and Hydrocortisone: 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
Fosphenytoin is converted to phenytoin, a strong inducer of CYP3A4 and other enzymes, which accelerates hydrocortisone metabolism. Glucocorticoid effect may be reduced, which matters in adrenal insufficiency or when treating inflammatory conditions. Hydrocortisone may also alter phenytoin levels unpredictably.
What this interaction means in plain words
Fosphenytoin and Hydrocortisone 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; Hydrocortisone belongs to Endocrine.
Why it happens
Phenytoin induces CYP3A4 and hepatic metabolism, increasing hydrocortisone clearance.
What to do
Monitor clinical response to hydrocortisone and increase the dose if needed, for example in adrenal insufficiency. Check phenytoin concentrations when starting or stopping the steroid.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Fosphenytoin and Hydrocortisone, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Hydrocortisone
- Hydrocortisone + Mifepristone Contraindicated
- Hydrocortisone + Poliovirus vaccine live oral trivalent Contraindicated
- Hydrocortisone + Smallpox vaccine live Contraindicated
- Adenovirus types 4 and 7 live + Hydrocortisone Major
- Aldesleukin + Hydrocortisone Major
- Aspirin + Hydrocortisone 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 Hydrocortisone?
MediHelp rates the interaction as moderate. Fosphenytoin and Hydrocortisone 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 is converted to phenytoin, a strong inducer of CYP3A4 and other enzymes, which accelerates hydrocortisone metabolism. Glucocorticoid effect may be reduced, which matters in adrenal insufficiency or when treating inflammatory conditions. Hydrocortisone may also alter phenytoin levels unpredictably.
How serious is the interaction between Fosphenytoin and Hydrocortisone?
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 hydrocortisone and increase the dose if needed, for example in adrenal insufficiency. Check phenytoin concentrations when starting or stopping the steroid.
What other medicines interact with Hydrocortisone?
MediHelp also lists interactions of Hydrocortisone with, for example, Mifepristone, Poliovirus vaccine live oral trivalent, Smallpox vaccine live. The full list is on the Hydrocortisone page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
