Drug & supplement interaction

Cajeput Oil + Meperidine, Promethazine

Meperidine, Promethazine brand names: Meprozine, Mepergan.

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

Cajeput Oil has a moderate interaction with Meperidine, Promethazine. Evidence from in vitro research suggests that cajeput leaf extract can inhibit cytochrome P450 2D6 (CYP2D6) by approximately 30%.

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

Cajeput Oil and Meperidine, Promethazine

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

Moderate

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

Why this applies to Meperidine, Promethazine

Meperidine, Promethazine falls under CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES — the group Cajeput Oil interacts with.

Evidence from in vitro research suggests that cajeput leaf extract can inhibit cytochrome P450 2D6 (CYP2D6) by approximately 30%. Theoretically, cajeput oil may increase levels of drugs metabolized by CYP2D6. Some drugs metabolized by CYP2D6 include amitriptyline (Elavil), clozapine (Clozaril), codeine, desipramine (Norpramin), donepezil (Aricept), fentanyl (Duragesic), flecainide (Tambocor), fluoxetine (Prozac), meperidine (Demerol), methadone (Dolophine), metoprolol (Lopressor, Toprol XL), olanzapine (Zyprexa), ondansetron (Zofran), tramadol (Ultram), trazodone (Desyrel), 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

This combination product pairs meperidine (a pain reliever) with promethazine (an antihistamine that calms nausea). Your liver uses an enzyme called CYP2D6 to help process both ingredients. Lab research hints that cajeput leaf extract can slow that enzyme by roughly 30 percent, so in theory the medication could clear a bit slower and build up more than expected.

If that happened, you might feel extra drowsy, dizzy, foggy, or notice slower breathing, since meperidine is a strong opioid. That said, this is based only on test-tube work, not real people, so the real-world risk is uncertain. Smelling or inhaling the oil briefly is unlikely to matter, but please check with your pharmacist or doctor before using concentrated cajeput products while on this medicine.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Subehan, Usia, T., Iwata, H., Kadota, S., and Tezuka, Y. Mechanism-based inhibition of CYP3A4 and CYP2D6 by Indonesian medicinal plants. J Ethnopharmacol. 5-24-2006;105(3):449-455. 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

Cajeput Oil Also Interacts With Other Medications

Cajeput Oil has 277 moderate known drug interactions in our database — the Meperidine, Promethazine one above is one of them. If you take anything else, check it against the full list below.

Moderate 277 No known interaction 2,553 (incl. Meperidine, Promethazine)
Taking anything else?

Check Another of Your Medications Against Cajeput Oil

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

Everything else you take

See Every Supplement That Interacts With Meperidine, Promethazine

This page covers Cajeput Oil only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Meperidine, Promethazine page lists 207 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 · 160 moderate · 37 minor.

From our pharmacist’s overview on the Meperidine, Promethazine page

“Meprozine combines meperidine, an opioid painkiller, with promethazine, a sedating antihistamine, so it already slows the brain on two fronts. I would read this list of 207 supplements and herbal ingredients with genuine care, starting with the 10 rated major.”

Reviewed by 2 · Jul 18, 2026

Open the Meperidine, Promethazine interaction page

How much people look this up

Where Cajeput Oil and Meperidine, Promethazine 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 Cajeput Oil
Top half

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

29 days ago today
Medication Meperidine, Promethazine
Steady interest

#2,405 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 Cajeput Oil

What is Cajeput Oil?

Cajeput Oil
  • Muscle and joint aches
  • Cough and congestion
  • Minor skin irritation
  • Insect repellent
  • Aromatherapy

Cajeput oil is an aromatic essential oil traditionally used for aches, congestion, and minor skin complaints, but solid human evidence for these uses is limited. Like other essential oils, it should never be swallowed and should be diluted before applying to skin; consult a pharmacist or doctor before use, especially in children, pregnancy, or breastfeeding.

Read the full Cajeput Oil monograph & all interactions
Keep checking

Other Drugs & Cajeput Oil

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

0Major
277Moderate
0Minor
2,552No known interaction
277 Moderate 2,552 No interaction
Moderate

277 interactions

Showing 60 of 277 moderate interactions — see all 277 on the Cajeput Oil page.

No interaction 2,552 drugs checked — show the list

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

Showing the 60 most looked-up of 2,552 medications checked with no known interaction — see the full Cajeput Oil list.

See the full Cajeput Oil interactions page
See every supplement checked against Meperidine, Promethazine, 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
Cajeput Oil monograph › Uses, safety, and every drug interaction in one place Meperidine, Promethazine supplement interactions › Every supplement checked against Meperidine, Promethazine, 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 Cajeput Oil and Meperidine, Promethazine Together: Common Questions

Can you take Cajeput Oil with Meperidine, Promethazine?
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 Cajeput Oil and Meperidine, Promethazine 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

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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.