Drug interactions
St john's wort + Zonisamide
Severity: Moderate
St john's wort and Zonisamide: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
St John's wort induces CYP3A4, which is the main enzyme that metabolises zonisamide. Zonisamide exposure may fall and seizure control may be reduced, particularly if the herbal product is started or stopped without the prescriber's knowledge.
What this interaction means in plain words
St john's wort and Zonisamide can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Induction of CYP3A4 by hyperforin increases zonisamide clearance.
What to do
Avoid the herbal product in patients with epilepsy where possible. If it is used, monitor seizure frequency and consider zonisamide dose adjustment, and re-evaluate the dose when St John's wort is stopped.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Zonisamide
- Zonisamide + Zuranolone Major
- Acetazolamide + Zonisamide Moderate
- Amisulpride + Zonisamide Moderate
- Amobarbital + Zonisamide Moderate
- Apalutamide + Zonisamide Moderate
- Asenapine transdermal + Zonisamide Moderate
Frequently asked questions
Can I take St john's wort with Zonisamide?
MediHelp rates the interaction as moderate. St john's wort and Zonisamide can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. St John's wort induces CYP3A4, which is the main enzyme that metabolises zonisamide. Zonisamide exposure may fall and seizure control may be reduced, particularly if the herbal product is started or stopped without the prescriber's knowledge.
How serious is the interaction between St john's wort and Zonisamide?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the herbal product in patients with epilepsy where possible. If it is used, monitor seizure frequency and consider zonisamide dose adjustment, and re-evaluate the dose when St John's wort is stopped.
What other medicines interact with Zonisamide?
MediHelp also lists interactions of Zonisamide with, for example, Zuranolone, Acetazolamide, Amisulpride. The full list is on the Zonisamide page.
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