Does Phenytoin Interact With Valproic Acid?

Name: Does Phenytoin Interact With Valproic Acid?
Creator: OmniRx Health

7 DRUG INTERACTIONS Hepatic enzyme-inducing drugs (e.g., phenytoin, carbamazepine, phenobarbital, primidone, rifampin) can increase valproate clearance, while enzyme inhibitors (e.g., felbamate) can decrease valproate clearance.

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

Severity: Minor

Severity basis: drug interactions section. Combining Phenytoin (Anticonvulsant) and Valproic Acid (Anticonvulsant / mood stabilizer) 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. Phenytoin is a anticonvulsant and Valproic Acid is a anticonvulsant / mood stabilizer; 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 Phenytoin and Valproic Acid, 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

7 DRUG INTERACTIONS Hepatic enzyme-inducing drugs (e.g., phenytoin, carbamazepine, phenobarbital, primidone, rifampin) can increase valproate clearance, while enzyme inhibitors (e.g., felbamate) can decrease valproate clearance.

Source: FDA structured product labeling (set_id 1286ab49-fa34-488e-e063-6394a90ad582).

Phenytoin

Anticonvulsant

Brands: Dilantin

View Phenytoin safety profile

Valproic Acid

Anticonvulsant / mood stabilizer

Brands: Depakote, Depakene

View Valproic Acid safety profile

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

Frequently Asked Questions

Can you take Phenytoin and Valproic Acid together?

Phenytoin and Valproic Acid 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 Phenytoin and Valproic Acid 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 Phenytoin and Valproic Acid?

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 Phenytoin Interactions

Other Valproic Acid Interactions

Sources & References

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