Hydantoins/Fluoxetine Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

Fluoxetine may change how quickly your body processes your seizure medicine.

What might happen:

The blood levels of your seizure medicine could change if fluoxetine is started or stopped.Seizure medicine blood levels may increase after fluoxetine is started, increasing your risk for adverse effects from your seizure medicine.If your fluoxetine is stopped, blood levels of your seizure medicine could fall. Lower levels of your seizure medicine could increase your risk for seizures.

What you should do about this interaction:

Let your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together.If you experience nausea, vomiting, confusion, dizziness, seizures, or other symptoms, contact your doctor. If your fluoxetine is discontinued, contact the doctor who prescribes your seizure medicine. It may be necessary to measure the blood levels of your seizure medicine more often or adjust the dose.Your healthcare professionals (e.g. doctor or pharmacist) may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

  • 1.Dilantin (phenytoin sodium) US prescribing information. Pfizer, Inc. November, 2016.
  • 2.US Food and Drug Administration (FDA). Drug Development and Drug Interactions: Table of Substrates, Inhibitors and Inducers. Available at: https://www.fda.gov/drugs/drug-interactions-labeling/drug-development-and- drug-interactions-table-substrates-inhibitors-and-inducers. Updated 11/14/2017.
  • 3.Prozac (fluoxetine hydrochloride) US prescribing information. Eli Lilly and Company October, 2014.
  • 4.Jalil P. Toxic reaction following the combined administration of fluoxetine and phenytoin: two case reports. J Neurol Neurosurg Psychiatry 1992 May;55(5):412-3.
  • 5.Woods DJ, Coulter DM, Pillans P. Interaction of phenytoin and fluoxetine. N Z Med J 1994 Jan 26;107(970):19.

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CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.