Drug & supplement interaction

Black Horehound + Zonisamide

Zonisamide brand names: Zonegran, Zonisade.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Black Horehound has a moderate interaction with Zonisamide. Theoretically, black horehound might have additive effects when used with dopamine agonists.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Black Horehound and Zonisamide

Here is the interaction we found between these two, with the evidence behind it.

Moderate

DOPAMINE AGONISTS

Why this applies to Zonisamide

Zonisamide falls under DOPAMINE AGONISTS — the group Black Horehound interacts with.

Theoretically, black horehound might have additive effects when used with dopamine agonists. Some constituents of black horehound bind to dopamine D2 receptors in vitro; however, this has not yet been reported in humans. Some dopamine agonists include bromocriptine (Parlodel), levodopa (Dopar, component of Sinemet), pramipexole (Mirapex), ropinirole (Requip), and others.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the honest picture: the interaction we have on file ties black horehound to dopamine agonists, drugs like pramipexole or levodopa. Zonisamide isn't really one of those. It's an anti-seizure medicine that calms overactive electrical signals in the brain, so the dopamine angle doesn't line up cleanly with how zonisamide works.

What little we know comes only from lab dish studies showing some black horehound compounds touch dopamine receptors. That has never been shown to matter in actual people, and it's a weak, theoretical signal. So I wouldn't expect a meaningful clash with your zonisamide. Still, both can affect the nervous system, so things like extra drowsiness or dizziness are worth watching. Please run it by your pharmacist or neurologist before adding it.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Daels-Rakotoarison DA, Seidel V, Gressier B, et al. Neurosedative and antioxidant activities of phenylpropanoids from Ballota nigra. Arzneimittelforschung 2000;50:16-23. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Black Horehound Also Interacts With Other Medications

Black Horehound has 22 moderate known drug interactions in our database — the Zonisamide one above is one of them. If you take anything else, check it against the full list below.

Moderate 22 No known interaction 2,808 (incl. Zonisamide)
Taking anything else?

Check Another of Your Medications Against Black Horehound

Covers the 2,830 medications we’ve checked against Black Horehound. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Zonisamide

This page covers Black Horehound only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Zonisamide page lists 206 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Grapefruit (major).

By severity: 9 major · 157 moderate · 40 minor.

From our pharmacist’s overview on the Zonisamide page

“Zonisamide (Zonegran, Zonisade) keeps seizures under control, which means anything that shifts its blood level or stacks extra sedation on top deserves real respect, and nine of the 206 supplement ingredients on file rate major. Two big themes run through nearly everything here.”

Reviewed by 2 · Jul 18, 2026

Open the Zonisamide interaction page

How much people look this up

Where Black Horehound and Zonisamide Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Black Horehound
Top half

#467 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Zonisamide
Top 25%

#635 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Black Horehound

What is Black Horehound?

Black Horehound
  • Nausea and vomiting
  • Anxiety and nervous tension
  • Sleep problems
  • Mild digestive upset
  • Coughs and respiratory complaints

Black horehound is a traditional European herb mainly used for nausea, mild anxiety, and digestive upset, but high-quality human studies are lacking, so its effectiveness is largely unproven. It has a strong, unpleasant smell and taste, and its safety has not been well studied, so it should be avoided in pregnancy and breastfeeding and used cautiously by everyone else.

Read the full Black Horehound monograph & all interactions
Medication

About Zonisamide

What Is Zonisamide Used For?

Brand names: Zonegran, Zonisade

Zonisamide is used as add-on therapy — meaning it is combined with other seizure medications, not used alone — to treat partial seizures (seizures that start in one part of the brain) in adults with epilepsy. Zonegran (capsule) and generic zonisamide capsules are approved for adults with epilepsy.

Zonisade (oral suspension) is approved as add-on therapy for partial-onset seizures in adults and in patients 16 years of age and older.

See full Zonisamide drug information
Keep checking

Other Drugs & Black Horehound

Browse every other medication we’ve checked against Black Horehound — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
22Moderate
0Minor
2,807No known interaction
22 Moderate 2,807 No interaction
Moderate

22 interactions

No interaction 2,807 drugs checked — show the list

We also checked Black Horehound against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,807 medications checked with no known interaction — see the full Black Horehound list.

See the full Black Horehound interactions page
See every supplement checked against Zonisamide, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Black Horehound monograph › Uses, safety, and every drug interaction in one place Zonisamide supplement interactions › Every supplement checked against Zonisamide, ranked by severity Zonisamide drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Black Horehound and Zonisamide Together: Common Questions

Can you take Black Horehound with Zonisamide?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Black Horehound and Zonisamide interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Zonisamide and Black Horehound?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.