Drug & supplement interaction

Thuja + Thioridazine

Thioridazine brand name: Mellaril.

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

Thuja has a moderate interaction with Thioridazine. Thuja products can contains significant amounts of thujone, a neurotoxin.

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

Thuja and Thioridazine

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

Moderate

SEIZURE THRESHOLD LOWERING DRUGS

Why this applies to Thioridazine

Thioridazine falls under SEIZURE THRESHOLD LOWERING DRUGS — the group Thuja interacts with.

Thuja products can contains significant amounts of thujone, a neurotoxin. Theoretically, patients taking drugs that lower the seizure threshold might be at greater risk of seizure if they also take thuja. Advise patients taking these drugs to avoid thuja products. Some drugs that lower the seizure threshold include anesthetics (propofol, others), antiarrhythmics (mexiletine), antibiotics (amphotericin, penicillin, cephalosporins, imipenem), antidepressants (bupropion, others), antihistamines (cyproheptadine, others), immunosuppressants (cyclosporine), narcotics (fentanyl, others), stimulants (methylphenidate), theophylline, 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 simple version: Thuja can contain thujone, a compound that may lower the brain's threshold for seizures. Thioridazine is one of those medicines that can already nudge that threshold down a bit on its own. Put the two together and, at least in theory, you could be at a slightly higher risk of a seizure.

I want to be honest about how solid this is: the concern is mostly theoretical and based on anecdotal reports, not strong human studies. Still, because thujone can be genuinely toxic in concentrated amounts, I'd play it safe and steer clear of thuja supplements and oils while you're on thioridazine. Please run it by your pharmacist or doctor before adding any thuja product.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Millet Y, Jouglard J, Steinmetz MD, et al. Toxicity of some essential plant oils. Clinical and experimental study. Clin Toxicol 1981;18:1485-98. 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

Thuja Also Interacts With Other Medications

Thuja has 575 moderate known drug interactions in our database — the Thioridazine one above is one of them. If you take anything else, check it against the full list below.

Moderate 575 No known interaction 2,255 (incl. Thioridazine)
Taking anything else?

Check Another of Your Medications Against Thuja

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

From our Q&A

Questions About Thuja or Thioridazine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Thuja or Thioridazine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Thioridazine

This page covers Thuja only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Thioridazine page lists 168 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Cesium (major) and Ephedra (major).

By severity: 11 major · 125 moderate · 32 minor.

From our pharmacist’s overview on the Thioridazine page

“Thioridazine (Mellaril) is an older antipsychotic already known for disturbing the heart's rhythm, and the supplements that worry me most here do the same thing, stretching the QT interval further. Grapefruit in large amounts sits in that group, alongside ephedra and several other major-rated entries.”

Reviewed by 2 · Jul 18, 2026

Open the Thioridazine interaction page

One more smart check

Taking Thuja as Part of a Dietary Supplement Product? Check It for Interactions

We hold 84 real supplement products containing Thuja, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Thuja. Your product may carry other ingredients that interact with Thioridazine too, on top of Thuja — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Thuja and Thioridazine 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 Thuja
Top half

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

29 days ago today
Medication Thioridazine
Steady interest

#2,479 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 Thuja

What is Thuja?

  • Warts and skin growths
  • Respiratory and immune support
  • Cold and upper respiratory symptoms
  • Topical skin conditions
  • Traditional use as a diuretic or to bring on menstruation

Thuja, also called northern white cedar or arborvitae, is a tree whose leaf and oil have a long history in folk and homeopathic medicine, especially for warts and immune support. Solid human evidence for these uses is very limited, and the undiluted oil contains thujone, which can be toxic. Talk with a pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Read the full Thuja monograph & all interactions
Medication

About Thioridazine

What Is Thioridazine Used For?

Brand name: Mellaril

Thioridazine Hydrochloride tablets are used for the management of schizophrenia — but only in patients who have already tried at least two other antipsychotic medications without adequate results, either because those drugs didn't work well enough or caused intolerable side effects.

Because thioridazine carries serious heart-rhythm risks, it is considered a last-resort option for schizophrenia, not a first-line treatment. It is not approved for dementia-related psychosis or any other psychiatric condition.

See full Thioridazine drug information
Keep checking

Other Drugs & Thuja

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

0Major
575Moderate
0Minor
2,254No known interaction
575 Moderate 2,254 No interaction
Moderate

575 interactions

Showing 60 of 575 moderate interactions — see all 575 on the Thuja page.

No interaction 2,254 drugs checked — show the list

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

Showing the 60 most looked-up of 2,254 medications checked with no known interaction — see the full Thuja list.

See the full Thuja interactions page
See every supplement checked against Thioridazine, 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
Thuja monograph › Uses, safety, and every drug interaction in one place Thioridazine supplement interactions › Every supplement checked against Thioridazine, ranked by severity Thioridazine 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 Thuja and Thioridazine Together: Common Questions

Can you take Thuja with Thioridazine?
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 Thuja and Thioridazine 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 Thioridazine and Thuja?

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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.