Drug & supplement interaction

Limonene + Atropine, Phenobarbital

Atropine, Phenobarbital brand name: Anthrocol.

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

Atropine, Phenobarbital falls into 2 drug categories that Limonene can interact with; the most serious is rated moderate. There's preliminary evidence that limonene might be a substrate for cytochrome P450 2C19 (CYP2C19).

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Limonene and Atropine, Phenobarbital

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Limonene interacts with whole categories of medication. Atropine, Phenobarbital falls into 2 of those categories, so it can interact with Limonene in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 2C19 (CYP2C19) INDUCERS

1 of 2

Why this applies to Atropine, Phenobarbital

Atropine, Phenobarbital falls under CYTOCHROME P450 2C19 (CYP2C19) INDUCERS — the group Limonene interacts with.

There's preliminary evidence that limonene might be a substrate for cytochrome P450 2C19 (CYP2C19). CYP2C19 inducers might decrease the effects of limonene. So far, this interaction has not been reported in humans. Inducers of CYP2C19 include carbamazepine (Tegretol), prednisone (Deltasone), and rifampin (Rifadin, Rimactane).
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 key thing to understand about this pairing: the interaction runs in one direction only, and it's the limonene that may take the hit, not your medication. The phenobarbital portion of this product is a known enzyme booster (it speeds up CYP2C19), and limonene happens to be processed by that same pathway. So in theory, phenobarbital could cause your body to clear limonene faster, leaving less of it around to do whatever you were hoping it would do.

The good news is this is very weak evidence, drawn from lab and animal work, and it has never actually been documented in people. Your atropine and phenobarbital effects (things like dry mouth, drowsiness, or seizure control) shouldn't change because of the limonene. Food amounts of citrus are a non-issue. Still, since phenobarbital is a serious medicine, run any concentrated limonene supplement by your pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Crowell PL. Prevention and therapy of cancer by dietary monoterpenes. J Nutr 1999;129:775S-778S. PubMed
  2. Miyazawa M, Shindo M, Shimada T. Metabolism of (+)- and (-)-limonenes to respective carveols and perillyl alcohols by CYP2C9 and CYP2C19 in human liver microsomes. Drug Metab Dispos 2002;30:602-7. PubMed
Moderate

CYTOCHROME P450 2C9 (CYP2C9) INDUCERS

2 of 2

Atropine, Phenobarbital also falls under CYTOCHROME P450 2C9 (CYP2C9) INDUCERS.

There's preliminary evidence that limonene might be a substrate for cytochrome P450 2C9 (CYP2C9). Inducers of CYP2C9 might decrease limonene levels. Inducers of CYP2C9 include rifampin (Rifadin, Rimactane) and secobarbital (Seconal).
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 key thing to understand about this pairing: the interaction runs in the opposite direction from what most people expect. Your medication isn't the one affected. The phenobarbital part is a known enzyme booster (it speeds up liver enzymes, including CYP2C9), and limonene appears to be broken down by that same enzyme. So in theory, phenobarbital could clear limonene out faster, leaving you with less of the supplement, not more.

In plain terms, your atropine/phenobarbital medicine should keep working normally, but your limonene may simply do less. The evidence here is only lab and animal data, so this is mostly theoretical, and small culinary amounts of citrus are very unlikely to matter. Before adding a concentrated limonene supplement, just run it past your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Crowell PL. Prevention and therapy of cancer by dietary monoterpenes. J Nutr 1999;129:775S-778S. PubMed
  2. Miyazawa M, Shindo M, Shimada T. Metabolism of (+)- and (-)-limonenes to respective carveols and perillyl alcohols by CYP2C9 and CYP2C19 in human liver microsomes. Drug Metab Dispos 2002;30:602-7. 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

Limonene Also Interacts With Other Medications

Limonene has 228 moderate known drug interactions in our database — the Atropine, Phenobarbital one above is among them. If you take anything else, check it against the full list below.

Moderate 228 No known interaction 2,602 (incl. Atropine, Phenobarbital)
Taking anything else?

Check Another of Your Medications Against Limonene

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

Everything else you take

See Every Supplement That Interacts With Atropine, Phenobarbital

This page covers Limonene only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Atropine, Phenobarbital page lists 165 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 Henbane (major).

By severity: 10 major · 134 moderate · 21 minor.

From our pharmacist’s overview on the Atropine, Phenobarbital page

“Anthrocol combines phenobarbital, a sedating barbiturate, with atropine, and I would treat its supplement interactions with genuine care rather than a quick skim. Nearly half the entries, alcohol in any form among them, deepen phenobarbital's sedation, at worst to the point of dangerously slowed breathing.”

Reviewed by 2 · Jul 18, 2026

Open the Atropine, Phenobarbital interaction page

One more smart check

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

We hold 89 real supplement products containing Limonene, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Limonene. Your product may carry other ingredients that interact with Atropine, Phenobarbital too, on top of Limonene — 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 Limonene and Atropine, Phenobarbital 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 Limonene
Steady interest

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

29 days ago today
Medication Atropine, Phenobarbital
Top 10%

#230 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 Limonene

What is Limonene?

  • Heartburn and acid reflux
  • Digestive upset
  • Stress and mood support
  • Antioxidant support
  • General wellness

Limonene is a natural compound found in the peel of citrus fruits like oranges and lemons, and it is used as a flavoring agent and dietary supplement. People take it for heartburn, digestion, and general wellness, but solid human evidence is limited. It is generally well tolerated in food amounts, but talk with your pharmacist or doctor before using concentrated supplements.

Read the full Limonene monograph & all interactions
Keep checking

Other Drugs & Limonene

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

0Major
228Moderate
0Minor
2,601No known interaction
228 Moderate 2,601 No interaction
Moderate

228 interactions

Showing 60 of 228 moderate interactions — see all 228 on the Limonene page.

No interaction 2,601 drugs checked — show the list

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

Showing the 60 most looked-up of 2,601 medications checked with no known interaction — see the full Limonene list.

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

Can you take Limonene with Atropine, Phenobarbital?
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.
Why are there 2 interactions listed for Limonene and Atropine, Phenobarbital?
Atropine, Phenobarbital belongs to more than one drug category, and Limonene interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Limonene and Atropine, Phenobarbital 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 Atropine, Phenobarbital and Limonene?

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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.