Drug interactions
Dexamethasone + Phenytoin
Severity: Moderate
Dexamethasone and Phenytoin: 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 accelerates dexamethasone clearance and can reduce its anti-inflammatory, antiemetic or anti-edema effect. Dexamethasone may also alter phenytoin levels unpredictably, so seizure control can be affected.
What this interaction means in plain words
Dexamethasone and Phenytoin 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.
Dexamethasone belongs to Endocrine; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and P-glycoprotein, increasing dexamethasone metabolism and efflux.
What to do
Monitor clinical response to dexamethasone and increase the dose if effect is inadequate. Check phenytoin levels when starting or stopping dexamethasone.
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 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 Dexamethasone
- Bcg vaccine live + Dexamethasone Contraindicated
- Dexamethasone + Mifepristone Contraindicated
- Dexamethasone + Rilpivirine Contraindicated
- Dexamethasone + Smallpox vaccine live Contraindicated
- Dexamethasone + Varicella virus vaccine live Contraindicated
- Dexamethasone + Yellow fever vaccine Contraindicated
Frequently asked questions
Can I take Dexamethasone with Phenytoin?
MediHelp rates the interaction as moderate. Dexamethasone and Phenytoin 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 accelerates dexamethasone clearance and can reduce its anti-inflammatory, antiemetic or anti-edema effect. Dexamethasone may also alter phenytoin levels unpredictably, so seizure control can be affected.
How serious is the interaction between Dexamethasone and Phenytoin?
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 dexamethasone and increase the dose if effect is inadequate. Check phenytoin levels when starting or stopping dexamethasone.
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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