Does Dexamethasone Interact With Phenytoin?
Hepatic Enzyme Inducers, Inhibitors and Substrates: Drugs which induce cytochrome P450 3A4 (CYP 3A4) enzyme activity (e.g., barbiturates, phenytoin, carbamazepine, rifampin) may enhance the metabolism of corticosteroids and require that the dosage of the corticosteroid be increased.
Severity: Minor
Severity basis: drug interactions section. Combining Dexamethasone (Systemic corticosteroid) and Phenytoin (Anticonvulsant) is classified as a minor interaction.
What to Do
This is generally a minor interaction, but review it with your pharmacist to be sure it is safe for you.
How This Interaction Works
Interactions like this one can happen when two medicines have overlapping effects, or when one changes how the other is absorbed, broken down, or cleared from the body. Dexamethasone is a systemic corticosteroid and Phenytoin is a anticonvulsant; together they are documented as a minor interaction. How much this matters depends on your dose, your other medications, and your overall health.
If You Take Both Medications
If you have been prescribed both Dexamethasone and Phenytoin, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
From the FDA Label
Hepatic Enzyme Inducers, Inhibitors and Substrates: Drugs which induce cytochrome P450 3A4 (CYP 3A4) enzyme activity (e.g., barbiturates, phenytoin, carbamazepine, rifampin) may enhance the metabolism of corticosteroids and require that the dosage of the corticosteroid be increased.
Source: FDA structured product labeling (set_id 01cfaa3e-5e30-18fa-e063-6394a90a084e).
Check these against your full medication list in our free Interaction Checker
Frequently Asked Questions
Can you take Dexamethasone and Phenytoin together?
Dexamethasone and Phenytoin have a documented minor interaction. This is generally a minor interaction, but review it with your pharmacist to be sure it is safe for you.
How serious is the Dexamethasone and Phenytoin interaction?
It is classified as a minor interaction, based on the FDA label's drug interactions section. A minor interaction is usually limited in effect but is still worth discussing with your care team.
What should I do if I'm taking both Dexamethasone and Phenytoin?
If you have been prescribed both Dexamethasone and Phenytoin, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
This information is educational — not medical advice.
This page is provided for general educational purposes and summarizes publicly available data from sources such as the U.S. Food & Drug Administration. It is not a substitute for the judgment of a licensed clinician and should not be used to start, stop, or change any medication. It may be incomplete or out of date, and individual circumstances vary. Always talk with your prescriber or pharmacist about your specific medications and health conditions. If you think you may have a medical emergency, call 911.
Other Dexamethasone Interactions
- Dexamethasone + Carbamazepine(moderate)
- Dexamethasone + Hydrocortisone(moderate)
- Dexamethasone + Itraconazole(moderate)
- Dexamethasone + Levothyroxine(moderate)
- Dexamethasone + Liothyronine(moderate)
- Dexamethasone + Aspirin(minor)
- Dexamethasone + Cyclosporine(minor)
- Dexamethasone + Indomethacin(minor)
- Dexamethasone + Ketoconazole(minor)
- Dexamethasone + Rifampin(minor)
- Dexamethasone + Warfarin(minor)
Other Phenytoin Interactions
- Phenytoin + Apixaban(major)
- Phenytoin + Itraconazole(major)
- Phenytoin + Methotrexate(major)
- Phenytoin + Rifampin(major)
- Phenytoin + Rivaroxaban(major)
- Phenytoin + Ticagrelor(major)
- Phenytoin + Amiodarone(moderate)
- Phenytoin + Atorvastatin(moderate)
- Phenytoin + Carbamazepine(moderate)
- Phenytoin + Carbidopa Levodopa(moderate)
- Phenytoin + Cholecalciferol(moderate)
- Phenytoin + Clarithromycin(moderate)
- Phenytoin + Cyclosporine(moderate)
- Phenytoin + Diazepam(moderate)
- Phenytoin + Digoxin(moderate)
- Phenytoin + Doxycycline(moderate)
- Phenytoin + Fluconazole(moderate)
- Phenytoin + Fluoxetine(moderate)
- Phenytoin + Folic Acid(moderate)
- Phenytoin + Furosemide(moderate)
- Phenytoin + Glimepiride(moderate)
- Phenytoin + Hydrocodone Acetaminophen(moderate)
- Phenytoin + Ketoconazole(moderate)
- Phenytoin + Lamotrigine(moderate)
- Phenytoin + Lithium(moderate)
- Phenytoin + Methylphenidate(moderate)
- Phenytoin + Methylprednisolone(moderate)
- Phenytoin + Mirtazapine(moderate)
- Phenytoin + Nifedipine(moderate)
- Phenytoin + Omeprazole(moderate)
- Phenytoin + Oxycodone(moderate)
- Phenytoin + Paroxetine(moderate)
- Phenytoin + Quetiapine(moderate)
- Phenytoin + Sertraline(moderate)
- Phenytoin + Simvastatin(moderate)
- Phenytoin + Tacrolimus(moderate)
- Phenytoin + Topiramate(moderate)
- Phenytoin + Tramadol(moderate)
- Phenytoin + Trazodone(moderate)
- Phenytoin + Sulfamethoxazole Trimethoprim(moderate)
- Phenytoin + Verapamil(moderate)
- Phenytoin + Warfarin(moderate)
- Phenytoin + Alprazolam(minor)
- Phenytoin + Atomoxetine(minor)
- Phenytoin + Azithromycin(minor)
- Phenytoin + Buprenorphine Naloxone(minor)
- Phenytoin + Bupropion(minor)
- Phenytoin + Canagliflozin(minor)
- Phenytoin + Clonazepam(minor)
- Phenytoin + Codeine(minor)
- Phenytoin + Gabapentin(minor)
- Phenytoin + Glipizide(minor)
- Phenytoin + Levothyroxine(minor)
- Phenytoin + Liothyronine(minor)
- Phenytoin + Metformin(minor)
- Phenytoin + Metronidazole(minor)
- Phenytoin + Modafinil(minor)
- Phenytoin + Ondansetron(minor)
- Phenytoin + Pregabalin(minor)
- Phenytoin + Sucralfate(minor)
- Phenytoin + Tadalafil(minor)
- Phenytoin + Valproic Acid(minor)