Does Itraconazole Interact With Phenytoin?

Name: Does Itraconazole Interact With Phenytoin?
Creator: OmniRx Health

Anticonvulsants Phenobarbital Phenytoin a Not recommended 2 weeks before and during itraconazole treatment.

Reviewed by the OmniRx Health clinical team•Last reviewed Jul 4, 2026

Severity: Major

Severity basis: drug interactions section (keywords: not recommended). Combining Itraconazole (Azole antifungal (strong CYP3A4 inhibitor)) and Phenytoin (Anticonvulsant) is classified as a major interaction.

What to Do

The label advises avoiding this combination or using it only under close medical supervision. Talk to your prescriber or pharmacist before combining them.

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. Itraconazole is a azole antifungal (strong cyp3a4 inhibitor) and Phenytoin is a anticonvulsant; together they are documented as a major 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 Itraconazole 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

Anticonvulsants Phenobarbital Phenytoin a Not recommended 2 weeks before and during itraconazole treatment.

Source: FDA structured product labeling (set_id 23126370-8d6a-4027-bd8f-860e2776ba3a).

Itraconazole

Azole antifungal (strong CYP3A4 inhibitor)

Brands: Sporanox, Tolsura

View Itraconazole safety profile

Phenytoin

Anticonvulsant

Brands: Dilantin

View Phenytoin safety profile

Check these against your full medication list in our free Interaction Checker

Frequently Asked Questions

Can you take Itraconazole and Phenytoin together?

Itraconazole and Phenytoin have a documented major interaction. The label advises avoiding this combination or using it only under close medical supervision. Talk to your prescriber or pharmacist before combining them.

How serious is the Itraconazole and Phenytoin interaction?

It is classified as a major interaction, based on the FDA label's drug interactions section (keywords: not recommended). A major interaction can cause serious harm and often calls for a change in therapy or close monitoring.

What should I do if I'm taking both Itraconazole and Phenytoin?

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.

Questions About Your Medications?

A licensed OmniRx provider can review your full medication list and help you understand what's safe for you — no office visit required.

Other Itraconazole Interactions

Other Phenytoin Interactions

Sources & References

Learn more about where our data comes from and how we write and review medical content.