Drug & supplement interaction

Eastern Red Cedar + Metharbital

Metharbital brand name: Gemonil.

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

Eastern Red Cedar has a minor interaction with Metharbital. In mice and rats given hexobarbital or pentobarbital, sleep time is reduced and metabolism of the drug is increased when they inhale essential oil vapor from Eastern red cedar wood chips in their bedding.

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

Eastern Red Cedar and Metharbital

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

Minor

BARBITURATES

Why this applies to Metharbital

Metharbital falls under BARBITURATES — the group Eastern Red Cedar interacts with.

In mice and rats given hexobarbital or pentobarbital, sleep time is reduced and metabolism of the drug is increased when they inhale essential oil vapor from Eastern red cedar wood chips in their bedding. Cedrol and cedrene in the essential oil are reported to induce liver microsomal enzymes. Theoretically, inhaling Eastern red cedar wood fragrance might reduce the efficacy of hexobarbital or pentobarbital in humans.
Severity Minor Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

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

Here's the gist with Eastern Red Cedar and your Metharbital (Gemonil), a barbiturate used to control certain seizures. The compounds in cedarwood oil, like cedrol, appear to rev up the liver enzymes that break down barbiturates. Since Metharbital is active on its own (not a prodrug), faster breakdown could mean your body clears it a bit quicker, potentially weakening its effect.

That said, I don't want to alarm you. This is purely theoretical and comes from rodents inhaling cedar bedding fumes, not from people. The interaction is rated minor and unlikely. Smelling a cedar closet or a few wood chips almost certainly won't change your seizure control. Still, before using concentrated cedar oil regularly, it's worth a quick chat with your doctor or pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  2. Johnson W. Final report on the safety assessment of Juniperus communis Extract, Juniperus oxycedrus Extract, Juniperus oxycedrus Tar, Juniperus phoenicea extract, and Juniperus virginiana Extract. Int J Toxicol 2001;20 Suppl 2:41-56. 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

Eastern Red Cedar Also Interacts With Other Medications

Eastern Red Cedar has 48 minor known drug interactions in our database — the Metharbital one above is one of them. If you take anything else, check it against the full list below.

Minor 48 No known interaction 2,782 (incl. Metharbital)
Taking anything else?

Check Another of Your Medications Against Eastern Red Cedar

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

Everything else you take

See Every Supplement That Interacts With Metharbital

This page covers Eastern Red Cedar only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metharbital page lists 97 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 Kava (major).

By severity: 7 major · 74 moderate · 16 minor.

Open the Metharbital interaction page

One more smart check

Taking Eastern Red Cedar as Part of a Dietary Supplement Product? Check It for Interactions

We hold 8 real supplement products containing Eastern Red Cedar, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Eastern Red Cedar. Your product may carry other ingredients that interact with Metharbital too, on top of Eastern Red Cedar — 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 Eastern Red Cedar and Metharbital 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 Eastern Red Cedar
Top half

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

29 days ago today
Medication Metharbital
Steady interest

#2,045 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 Eastern Red Cedar

What is Eastern Red Cedar?

  • Insect repellent
  • Aromatherapy and relaxation
  • Skin and minor wound care (topical, traditional)
  • Respiratory or congestion relief (traditional)
  • Antimicrobial and antifungal (lab-based interest)

Eastern Red Cedar is a North American evergreen tree whose wood and aromatic oil have long been used for fragrance, insect repelling, and folk remedies. Solid human research on its health benefits is very limited, and the essential oil can be toxic if swallowed, so it is mainly used externally or for aroma. Talk to a pharmacist or doctor before using it, especially during pregnancy or breastfeeding.

Read the full Eastern Red Cedar monograph & all interactions
Keep checking

Other Drugs & Eastern Red Cedar

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

0Major
0Moderate
48Minor
2,781No known interaction
48 Minor 2,781 No interaction
Minor

48 interactions

No interaction 2,781 drugs checked — show the list

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

Showing the 60 most looked-up of 2,781 medications checked with no known interaction — see the full Eastern Red Cedar list.

See the full Eastern Red Cedar interactions page
See every supplement checked against Metharbital, 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
Eastern Red Cedar monograph › Uses, safety, and every drug interaction in one place Metharbital supplement interactions › Every supplement checked against Metharbital, 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 Eastern Red Cedar and Metharbital Together: Common Questions

Can you take Eastern Red Cedar with Metharbital?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Eastern Red Cedar and Metharbital interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Metharbital and Eastern Red Cedar?

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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.