Drug & supplement interaction

Thuja + Ampicillin

Ampicillin brand names: Principen, Omnipen-N, Omnipen, Rimacillin, Penbritin.

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

Thuja has a moderate interaction with Ampicillin. 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 Ampicillin

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

Moderate

SEIZURE THRESHOLD LOWERING DRUGS

Why this applies to Ampicillin

Ampicillin 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 deal with combining Thuja and ampicillin. Thuja's leaf and oil contain thujone, a compound that can irritate the nervous system and, in high amounts, may make seizures more likely. Ampicillin, like other penicillin antibiotics, can itself slightly lower the seizure threshold, especially at high doses or in people whose kidneys aren't clearing it well. The worry is that stacking the two could theoretically nudge that risk up a bit higher.

I want to be honest about the evidence here: this is theoretical and based only on anecdotal reports, not solid studies. For most people taking a normal course of ampicillin, the chance of a problem is low. Still, since concentrated thuja products carry a real toxin, the safe move is to avoid them while on this antibiotic. Check with your pharmacist or doctor first.

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 Ampicillin 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. Ampicillin)
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 Ampicillin

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 Ampicillin, 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 Ampicillin

This page covers Thuja only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Ampicillin page lists 50 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Bacillus Coagulans (moderate), Bacillus Subtilis (moderate), Bifidobacterium Animalis Subsp. Lactis (moderate) and Bifidobacterium Bifidum (moderate).

By severity: 1 major · 39 moderate · 10 minor.

From our pharmacist’s overview on the Ampicillin page

“An antibiotic only works if enough of it survives the trip through your gut, and that is where ampicillin (Principen, Penbritin) meets real trouble with one supplement in particular. Activated charcoal, the single major-rated entry among the 50 on this page, binds drugs in the digestive tract and can sharply cut how much ampicillin you…”

Reviewed by 2 · Jul 18, 2026

Open the Ampicillin 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 Ampicillin 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 Ampicillin 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

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

29 days ago today
Medication Ampicillin
Top half

#890 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 Ampicillin

What Is Ampicillin Used For?

Brand names: Principen, Omnipen-N, Omnipen, Rimacillin, Penbritin

Ampicillin treats bacterial infections caused by susceptible organisms. It is used for respiratory tract infections, urinary tract infections, gastrointestinal infections (including typhoid fever and dysentery), bacterial meningitis (infection of the membranes surrounding the brain and spinal cord), and serious bloodstream infections such as septicemia and endocarditis (infection of the heart's inner lining).

Ampicillin capsules (oral form) are also indicated for genitourinary tract infections, including gonorrhea caused by non-penicillinase-producing organisms, and meningitis caused by N. meningitidis. The injectable forms (intramuscular or intravenous) are reserved for moderately severe to severe infections or for patients who cannot take oral medication.

See full Ampicillin 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 Ampicillin, 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 Ampicillin supplement interactions › Every supplement checked against Ampicillin, ranked by severity Ampicillin 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 Ampicillin Together: Common Questions

Can you take Thuja with Ampicillin?
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 Ampicillin 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 Ampicillin 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.