Primidone/Hydantoins 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:

The cause of the interaction is not known. When these two medicines are taken together, your body may not process primidone properly.

What might happen:

Primidone is converted by your body to phenobarbital. Your blood levels of phenobarbital may increase and cause toxic effects.

What you should do about this interaction:

Contact your doctor as soon as possible if you experience confusion, difficulty sleeping, difficulty breathing, very slow breathing, fainting, or rash. Contact your healthcare professionals (e.g. doctor or pharmacist) if you experience continued or bothersome dizziness, drowsiness, lightheadedness, clumsiness, or excessive daytime drowsiness.Your healthcare professionals may already be aware of this drug interaction and may be monitoring you for it. If your doctor prescribes these medicines together, it may be necessary to check the phenobarbital levels in your blood more often. Do not start, stop, or change the dosage of any medicine before checking with them first.

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  • 2.Wilson JT, Wilkinson GR. Chronic and severe phenobarbital intoxication in a child treated with primidone and diphenylhydantoin. J Pediatr 1973 Sep; 83(3):484-9.
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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.