Drug & supplement interaction

Phellodendron + acetaminophen, dextromethorphan, doxylamine

acetaminophen, dextromethorphan, doxylamine brand name: NyQuil.

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

acetaminophen, dextromethorphan, doxylamine falls into 2 drug categories that Phellodendron can interact with; the most serious is rated moderate. Theoretically, phellodendron might increase the sedative effects of CNS depressants.

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

Phellodendron and acetaminophen, dextromethorphan, doxylamine

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

Why Are There 2 Interactions?

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

Moderate

CNS DEPRESSANTS

1 of 2

Why this applies to acetaminophen, dextromethorphan, doxylamine

acetaminophen, dextromethorphan, doxylamine falls under CNS DEPRESSANTS — the group Phellodendron interacts with.

Theoretically, phellodendron might increase the sedative effects of CNS depressants.
Phellodendron contains berberine. Animal research suggests that berberine may have sedative effects. Theoretically, phellodendron might also have CNS depressants effects.
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 gist with NyQuil and Phellodendron. NyQuil already contains two ingredients that can make you drowsy: doxylamine (an antihistamine) and dextromethorphan (the cough suppressant). Phellodendron, mainly because of its berberine, has shown mild sedative effects in animal studies. So the worry is that stacking the two could leave you feeling extra sleepy, groggy, dizzy, or slow to react.

I want to be honest about the strength of this concern. It's theoretical, based on how these things work rather than solid human studies, so it may not amount to much for most people. Still, since NyQuil knocks plenty of folks out on its own, I'd be cautious about driving or mixing in alcohol, and check with your pharmacist before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Janbaz KH, Gilani AH. Studies on preventive and curative effects of berberine on chemical-induced hepatotoxicity in rodents. Fitoterapia 2000;71:25-33.. PubMed
  2. Shanbhag, S. M., Kulkarni, H. J., and Gaitonde, B. B. Pharmacological actions of berberine on the central nervous system. Jpn.J Pharmacol 1970;20(4):482-487. PubMed
  3. Peng, W. H., Hsieh, M. T., and Wu, C. R. Effect of long-term administration of berberine on scopolamine-induced amnesia in rats. Jpn J Pharmacol 1997;74(3):261-266. DOI
  4. Sabir M and Bhide NK. Study of some pharmacological actions of berberine. Ind J Physiol & Pharmac 1971;15(3):111-132.
Moderate

DEXTROMETHORPHAN (Robitussin DM, others)

2 of 2
Theoretically, phellodendron may increase serum levels of dextromethorphan.
Phellodendron contains berberine. Preliminary clinical research shows that berberine can inhibit cytochrome P450 2D6 (CYP2D6) activity and reduce the metabolism of dextromethorphan. Theoretically, phellodendron may also inhibit the metabolism of dextromethorphan.
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 gist for your NyQuil question. One of its ingredients, dextromethorphan (the cough suppressant), is cleared from your body by a liver enzyme called CYP2D6. Phellodendron contains berberine, which lab and early human studies suggest can slow that enzyme down. In theory, that means dextromethorphan could build up a bit higher than usual.

If that happens, you might feel more of dextromethorphan's effects, things like extra drowsiness, dizziness, or a foggy, lightheaded feeling. Keep in mind NyQuil already contains doxylamine, which is sedating on its own, so the sleepiness could stack up. This is a theoretical concern based on how these compounds behave, not something proven in real-world use. Still, 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. Guo, Y., Chen, Y., Tan, Z. R., Klaassen, C. D., and Zhou, H. H. Repeated administration of berberine inhibits cytochromes P450 in humans. Eur J Clin Pharmacol 2012;68(2):213-217. 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

Phellodendron Also Interacts With Other Medications

Phellodendron has 1,159 moderate known drug interactions in our database — the acetaminophen, dextromethorphan, doxylamine one above is among them. If you take anything else, check it against the full list below.

Moderate 1,159 No known interaction 1,671 (incl. acetaminophen, dextromethorphan, doxylamine)
Taking anything else?

Check Another of Your Medications Against Phellodendron

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

Everything else you take

See Every Supplement That Interacts With acetaminophen, dextromethorphan, doxylamine

This page covers Phellodendron only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the acetaminophen, dextromethorphan, doxylamine page lists 106 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 Grapefruit (major).

By severity: 8 major · 78 moderate · 20 minor.

From our pharmacist’s overview on the acetaminophen, dextromethorphan, doxylamine page

“NyQuil (acetaminophen, dextromethorphan, doxylamine) is designed to make you drowsy, and that is exactly where most of its supplement interactions live. Seventy-eight of the 106 ingredients on this list add to its sedation, and the eight rated major, alcohol and kava among them, can push a nighttime cold remedy toward serious depressio…”

Reviewed by 2 · Jul 18, 2026

Open the acetaminophen, dextromethorphan, doxylamine interaction page

One more smart check

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

We hold 393 real supplement products containing Phellodendron, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Phellodendron. Your product may carry other ingredients that interact with acetaminophen, dextromethorphan, doxylamine too, on top of Phellodendron — 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 Phellodendron and acetaminophen, dextromethorphan, doxylamine 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 Phellodendron
Top 25%

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

29 days ago today
Medication acetaminophen, dextromethorphan, doxylamine
Top 5%

#66 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 Phellodendron

What is Phellodendron?

Phellodendron
  • Digestive complaints and diarrhea
  • Inflammation and joint discomfort
  • Stress and weight management (in combination products)
  • Skin conditions (topical, traditional)
  • Antimicrobial support

Phellodendron is a traditional Chinese medicine bark (Huang Bai) that contains berberine and other plant compounds with antimicrobial and anti-inflammatory activity in lab studies. Human evidence for most uses is limited, and it is often sold in combination with other herbs, making its individual effects hard to judge. Talk with your pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Read the full Phellodendron monograph & all interactions
Keep checking

Other Drugs & Phellodendron

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

0Major
1,159Moderate
0Minor
1,670No known interaction
1,159 Moderate 1,670 No interaction
Moderate

1,159 interactions

Showing 60 of 1,159 moderate interactions — see all 1,159 on the Phellodendron page.

No interaction 1,670 drugs checked — show the list

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

Showing the 60 most looked-up of 1,670 medications checked with no known interaction — see the full Phellodendron list.

See the full Phellodendron interactions page
See every supplement checked against acetaminophen, dextromethorphan, doxylamine, 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
Phellodendron monograph › Uses, safety, and every drug interaction in one place acetaminophen, dextromethorphan, doxylamine supplement interactions › Every supplement checked against acetaminophen, dextromethorphan, doxylamine, 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 Phellodendron and acetaminophen, dextromethorphan, doxylamine Together: Common Questions

Can you take Phellodendron with acetaminophen, dextromethorphan, doxylamine?
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 Phellodendron and acetaminophen, dextromethorphan, doxylamine?
acetaminophen, dextromethorphan, doxylamine belongs to more than one drug category, and Phellodendron 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 Phellodendron and acetaminophen, dextromethorphan, doxylamine 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.