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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