Drug & supplement interaction

Cajeput Oil + Acetaminophen, Dextromethorphan, Pseudoephedrine

Acetaminophen, Dextromethorphan, Pseudoephedrine brand names: Alka-Seltzer PLUS Flu Liquid Gels, Tylenol Flu Daytime Ex Strength, Non Aspirin Cold Caps, Tylenol Cold, Tylenol Flu Ex Strength.

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

Cajeput Oil has a moderate interaction with Acetaminophen, Dextromethorphan, Pseudoephedrine. 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 Acetaminophen, Dextromethorphan, Pseudoephedrine

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

Moderate

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

Why this applies to Acetaminophen, Dextromethorphan, Pseudoephedrine

Acetaminophen, Dextromethorphan, Pseudoephedrine 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

In this combo product, the piece that matters here is the dextromethorphan, the cough suppressant. Your body relies on a liver enzyme called CYP2D6 to break it down. Lab research hints that cajeput oil may slow that enzyme by roughly 30 percent, which could let dextromethorphan build up a bit. If that happened, you might feel more drowsy, dizzy, or notice mild stomach upset. The acetaminophen and pseudoephedrine pieces aren't really affected by this pathway.

Keep this in perspective. This is based only on test-tube work, not real people, so the actual risk is likely small, especially with short-term cold use. Still, since cold products and essential oils both vary, it's worth a quick chat with your pharmacist before combining them.

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 Acetaminophen, Dextromethorphan, Pseudoephedrine 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. Acetaminophen, Dextromethorphan, Pseudoephedrine)
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 Acetaminophen, Dextromethorphan, Pseudoephedrine

This page covers Cajeput Oil only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Acetaminophen, Dextromethorphan, Pseudoephedrine page lists 262 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Beer (major), Ephedra (major) and Grapefruit (major).

By severity: 12 major · 207 moderate · 43 minor.

From our pharmacist’s overview on the Acetaminophen, Dextromethorphan, Pseudoephedrine page

“Ephedra is the ingredient to notice first here. Pseudoephedrine, the decongestant in Tylenol Flu, Alka-Seltzer PLUS Flu, and other acetaminophen, dextromethorphan, and pseudoephedrine combinations, is itself a stimulant, and 44 entries push the same direction, raising the odds of high blood pressure and a racing heart.”

Reviewed by 2 · Jul 18, 2026

Open the Acetaminophen, Dextromethorphan, Pseudoephedrine interaction page

How much people look this up

Where Cajeput Oil and Acetaminophen, Dextromethorphan, Pseudoephedrine 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
Steady interest

#1,362 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Acetaminophen, Dextromethorphan, Pseudoephedrine
Top 25%

#367 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 Acetaminophen, Dextromethorphan, Pseudoephedrine, 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 Acetaminophen, Dextromethorphan, Pseudoephedrine supplement interactions › Every supplement checked against Acetaminophen, Dextromethorphan, Pseudoephedrine, 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 Acetaminophen, Dextromethorphan, Pseudoephedrine Together: Common Questions

Can you take Cajeput Oil with Acetaminophen, Dextromethorphan, Pseudoephedrine?
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 Acetaminophen, Dextromethorphan, Pseudoephedrine 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 Acetaminophen, Dextromethorphan, Pseudoephedrine and Cajeput Oil?

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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.